Medical device and system having such a device

ABSTRACT

A medical device, having a body that is tubular at least in some sections. The body can be transferred from a compressed state into an expanded state and has a circumferential wall having at least one first lattice structure and one second lattice structure. The first lattice structure and the second lattice structure form separate layers of the circumferential wall, which are arranged coaxially one inside the other and connected to each other at least at points in such a way that the first lattice structure and the second lattice structure can be moved relative to each other at least in some sections. A system having such a device is also disclosed.

The invention relates to a medical device according to the preamble ofclaim 1. The invention further relates to a system having such a device.A device of the type in question is known from DE 601 28 588 T2, forexample.

DE 601 28 588 T2 discloses a stent whose tubular structure is formed bya plurality of layers. The individual layers each comprise a wire braid,the wire braids being interwoven. The wire braids of the individuallayers are therefore in each case woven with the wire braid of anadjacent layer and thus form a connection between the layers that coversa large surface area. This results overall in a relatively complexbraided structure of the wall of the stent.

The complex braided structure increases the fine mesh of the knownstent, and this is intended to have advantages in the treatment ofaneurysms. Specifically, the stent is used to impede the flow of bloodinto an aneurysm, by means of the stent being placed in a blood vesselin the area of an aneurysm. For this purpose, the stent is guided in aconventional manner known per se to the treatment site via a deliverysystem. The stent lies in a compressed state inside the delivery system.In other words, the stent has a minimal cross-sectional diameter in thedelivery system. In the area of the treatment site, the stent isreleased from the delivery system. The stent is in particular expandedor widened at the treatment site, such that the stent bears on thevessel wall of the blood vessel. The expansion can take placeautomatically (self-expandable stents) or with the aid of a balloon ofthe delivery system (balloon-expandable stents).

The known stent has disadvantages. The complex braided structure, inwhich the individual wire elements are interwoven over a plurality oflayers of the walls, means that, when the known stent is in thecompressed state, the individual wires inside the delivery system are inan arrangement that requires a large amount of space. This arrangementis seen particularly in the cross section of the compressed known stent,which is shown by way of example in FIG. 6 a. Here, the first wires 41of a first braid layer have a larger cross-sectional diameter than thesecond wires 42 of a second braid layer. The first wires 41 of the firstbraid layer are interwoven with the second wires 42 of the second braidlayer. In the compressed state, this results in the bulky arrangement asper FIG. 6 a. Relatively large free spaces between the first and secondwires 41, 42 remain unused, such that the known stent, in the compressedstate, has a relatively large overall cross-sectional diameter. Thisalso influences the minimum possible cross-sectional diameter for thedelivery system. Delivery of the known stent into quite small vessels isthus made more difficult.

As a result of the interweaving of the individual layers, theflexibility of the known stent is also adversely affected. Inparticular, the interwoven wires become blocked on each other, such thatthe known stent has a comparatively high degree of stiffness or lowflexibility.

In general, aneurysms in blood vessels are affected by various physicalphenomena that can lead to an enlargement or even a rupture of theaneurysm. These physical phenomena, arising from the physiology of thecardiovascular system, comprise, on the one hand, the transfer of theblood pressure into the aneurysm and, on the other hand, shear stresseswhich are caused by a flow of blood inside the aneurysm, and also localloads which act on the aneurysm wall or aneurysm neck and are causedwhen individual areas of the aneurysm are attacked directly by the bloodflow.

Aneurysms mostly form in arteries, i.e. blood vessels leading away fromthe heart. On account of the pulsating pump action of the heart, theblood flow in arteries is subject to intense fluctuations of pressure.The maximum pressure peaks in the arterial system occur in the ejectionphase of the heart, the systole. A pressure minimum is reached in thediastole, the filling phase of the heart chambers. The level of thelocal pressure within defined sections of the vessels is determined by,among other things, the compliance, i.e. the elasticity, of the vesselwall. The pressure fluctuations in the vessel are transferred throughthe aneurysm neck into the aneurysm. If untreated, the pressure insidethe blood vessel is transferred almost completely into the aneurysm,which leads to increased loading of the already weakened aneurysm wall.There is a danger of the aneurysm rupturing. The flow of blood from theblood vessel into the aneurysm is impeded by the use of known stents,for example the aforementioned stent according to DE 601 28 588 T2. Athrough-flow resistance is thus created which reduces the velocity ofthe flow of the blood into the aneurysm. Therefore, during the systole,the pressure inside the aneurysm rises more slowly and to a lesserdegree than inside the blood vessel. In other words, the transfer ofpressure from the blood vessel into the aneurysm through the meshes ofthe stent is delayed and incomplete. FIG. 1 c shows an example of thepressure profile of the blood pressure in the blood vessel (solid line)and the pressure curve of the blood pressure inside the aneurysm (brokenline).

It is known from practice that, some hours or days after an aneurysm hasbeen treated with known stents that impede the transfer of pressure intothe aneurysm, fissures can appear in the aneurysm wall and lead tobleeding. In the treatment of aneurysms with the known stents, there istherefore still the danger of the aneurysm rupturing.

It is assumed that, when the aneurysm is covered by known stents thatinfluence the blood pressure in the aneurysm, the cells of the aneurysmwall, including muscle cells in the area of the muscle layer (tunicamedia) of the vessel wall, degenerate as a result of the diminishingload. In other words, the cells of the aneurysm wall are used to thehigh pressure load. When the high pressure load is lost, degenerativeprocesses can set in, as a result of which the mechanical properties ofthe vessel wall may undergo negative changes. The danger of a rupture ofthe vessel wall in the aneurysm region thus increases.

The blood flow inside an aneurysm is subject to a further physicalphenomenon. As the blood in the blood vessel flows past the aneurysmneck, shear forces act at the interface between the blood in the bloodvessel and the blood inside the aneurysm. The resulting shear stressescause eddying of the blood inside the aneurysm. A flow eddy thus formsin the aneurysm. The eddy formation in the aneurysm prevents bloodclotting inside the aneurysm. In particular, the eddy formation preventsareas of stasis from developing, which are seen as a precondition foragglomeration in the form of so-called rouleaux formation. Theexpression rouleaux formation, or pseudoagglutination, designates thereversible formation of chain-like stacks of red blood cells. Withregard to the aforementioned degeneration of cells of the aneurysm wall,the obstruction of a tangential blood flow, which on account of shearstresses leads to an eddying of the blood flow inside the aneurysm, isregarded as disadvantageous. Up to a certain point, however, reductionof the shear stress is necessary to ensure that the blood can clot.However, if the reduction is too great, thrombus development takes placetoo rapidly. The fresh clot developing as a result of the blood stasisrapidly increases in volume, which can lead to fissures in the aneurysmwall.

Aneurysms in curved blood vessel sections have a further peculiarity interms of the way they are influenced by the blood flow in the bloodvessel. The curved shape of the vessel causes the blood in the bloodvessel to be deflected in a curved trajectory. When an aneurysm developsat the apex of the curve, a flow component of the blood flow ariseswhich is oriented substantially directly into the aneurysm, inparticular onto the aneurysm neck. The blood from the blood vessel thusflows directly into the aneurysm. As soon as the inflowing blood strikesthe aneurysm wall, particularly in the aneurysm head, the blood flow isdeflected, as a result of which the kinetic flow energy of the blood isconverted into a local pressure that locally stresses the aneurysm wall.The local inflow, and the local pressure resulting from the latter, can,in conjunction with the physiological pressure wave triggered by thesystole and the diastole, be the cause of the development of theaneurysm. A reduction of the pressure wave can be positive in order toprevent the aneurysm growing any further, or even in order to achieveshrinkage of the aneurysm. On the other hand, the reduction can have adisadvantageous effect on the degeneration of the cells of the aneurysmwall.

By means of known stents that cover the aneurysm neck, the localpressure caused by the direct inflow of blood into the aneurysm isreduced or avoided, since the blood flow through the stent placed in thevessel is deflected into the predetermined curved trajectory. Thefraction of the flow component routed directly into the aneurysm is thusreduced. At the same time, the known stents avoid the transfer of apressure wave into the aneurysm, as a result of which the degenerationof the cells of the aneurysm wall is promoted.

Another possible way of avoiding direct flow onto an aneurysm is toinfluence the vessel curvature. For example, the radius of curvature ofthe vessel in the area of the aneurysm can be reduced by a suitablestent. A precondition for this is a stent structure that has sufficientstiffness or radial strength to ensure that the stent structure forcesthe blood vessel into a more elongate and less curved shape.

In practice, the above-described medical requirements concerning thetreatment of aneurysms are satisfied by a number of different technicalapproaches. On the one hand, it is assumed that a very fine mesh, i.e.the smallest possible mesh size, of an aneurysm stent permits efficienttreatment. The very fine mesh is usually obtained using a large numberof wires. In order to achieve suitable crimpability, such that theaneurysm stent can be inserted into small blood vessels, the individualwires have a comparatively small cross-sectional diameter. Therefore,stents of this kind develop a comparatively low radial force. This meansthat stents of this kind do not permit any influence of the curvature ofa blood vessel. Moreover, stents with a low radial force have lowstability, which results in the danger of the stent moving away from itsoriginal position inside the blood vessel on account of the blood flowor the pulsation. There is therefore the danger of dislocation of thestent. In particular, cases are known from practice in which theinserted stents have migrated out of the blood vessel into the aneurysmand have caused further damage there. On account of the comparativelylow radial force, stents of this kind also have a relatively smallrestoring force. Frictional forces between the stent and the vessel wallcan mean that it is not possible to ensure an adaptation of thecross-sectional diameter of the stent to the cross-sectional diameter ofthe blood vessel, particularly under the influence of the systole anddiastole. With large braiding angles, the lattice structure can easilysquash together. As a result, the cells become smaller and the latticestructure becomes tighter. The permeability decreases, and thethrough-flow resistance increases, which can impair the flow conditionsand can lead to occlusion of side branches of the vessels.

In the known stents, the comparatively fine mesh is also achievedthrough a large braiding angle. A large braiding angle also increasesthe foreshortening. Foreshortening is understood as a phenomenon inwhich the lattice structure of the stent shortens in the axial directionduring the expansion, i.e. during the transfer from the compressed stateto the expanded state. A large braiding angle causes a quiteconsiderable shortening of the stent during the expansion. Thepositioning of such stents is made more difficult. There is the dangerof the stent being wrongly positioned. The effect of the foreshorteningis also seen in connection with the change of cross section of the bloodvessel during the systole and diastole. Even with comparatively smallchanges of diameter, the stent with a large braiding angle canexperience considerable lengthening or shortening. This also causes achange in the cell configuration and in the mesh size of the stent. Thereproducibility of the treatment is thus made more difficult. By meansof a large braiding angle, a high degree of flexibility is madeavailable in the known stent. However, with flexible stents of thiskind, the elongation of a curved blood vessel in order to reduce theimpulse on the aneurysm wall is not possible.

A further disadvantage of stents known from practice is that the stentsnarrow at least in some sections during elongation. Such an elongationof the stent in the axial direction can be caused by the sequence ofsystole and diastole. During the systole, the vessel diameter is wideneddepending on the vessel compliance. Moreover, an axial elongation of theblood vessel takes place at the same time. The axial ends of a stentwhich is positioned inside the blood vessel, and which bears on thevessel wall, move away from each other during the elongation of thevessel. According to the foreshortening effect, the elongation of thestent causes at least in some sections a reduction of the stentdiameter. The stent structure can then lift away from the aneurysm orfrom the aneurysm neck, as a result of which the effect of influencingthe flow is reduced. Moreover, a narrowing of the stent diameter,triggered by an elongation of the stent, can cause the contact betweenstent and vessel wall to be reduced, with the resulting danger ofdislocation of the stent.

The object of the invention is to make available a medical device whichpermits efficient treatment of aneurysms and has improved crimpability.In particular, the device is intended to prevent a postoperative ruptureof the aneurysm or a postoperative weakening of the aneurysm wall. It isalso the object of the invention to make available a system having sucha device.

According to the invention, this object is achieved, in respect of thedevice, by the subject matter of claim 1, and, in respect of the system,by the subject matter of claim 20.

The invention is based on the concept of making available a medicaldevice, comprising a body which is tubular at least in some sections,can be transferred from a compressed state to an expanded state and hasa circumferential wall with at least a first lattice structure and asecond lattice structure. The first lattice structure and the secondlattice structure form separate layers of the circumferential wall. Theseparate layers of the circumferential wall are arranged coaxially oneinside the other. Moreover, the separate layers of the circumferentialwall are connected to each other at least at points, in such a way thatthe first lattice structure and the second lattice structure are movablerelative to each other at least in some sections.

According to the invention, the first lattice structure and the secondlattice structure form separate layers of the circumferential wall.Therefore, the lattice structures are not connected to each other over alarge surface area, as they are in the prior art. Instead, theconnection between the lattice structures is punctiform, such that arelative movement is permitted between the layers or lattice structures.

Punctiform connection means that the area of the two lattice structureswhere they are arranged loosely on each other is greater in terms ofsurface area than the at least one connection area or the punctiformconnection areas between the two lattice structures, in such a way thata relative movement is possible between the two lattice structures. Theat least one connection area or the punctiform connection areas do notform a continuous lattice structure. Instead, the connection area islocally limited. For example, the connection area can in each casecomprise individual cells or meshes of the two lattice structures in thearea of which the mechanical connection exists. The punctiformconnection area can be limited to at most 4 cells or meshes of the firstand/or second lattice structure, wherein either 4 or fewer cells of thefirst lattice structure are connected to any desired number of cells, inparticular to more than 4 cells, of the second lattice structure. Thesame applies conversely for the second lattice structure. It is alsopossible that both lattice structures are connected to each other in thearea of at most 4 cells. The connection with 3 or 2 cells is disclosedexplicitly. The punctiform connection can also comprise, for example,the connection of individual lattice elements of the two latticestructures, in particular lattice filaments made of plastic or metal,for example lattice wires and/or strands composed of several filaments,or wires, which can be twisted together or parallel alongside eachother, i.e. not twisted together.

A punctiform connection is therefore understood as a connection limitedto a partial area or a partial surface of the lattice structure, whereinin particular the ratio between the surface area of the connectedlattice structures and the surface area of the free lattice structuresis such that the lattice structures can move relative to each other inthe free area, in particular can move relative to each other unimpeded.The surface area of the connected lattice structures is smaller than thesurface area of the free lattice structures. The at least one punctiformconnection can be arranged within the lattice structure. The punctiformconnection has an areal extent (one or more connection points) or alinear extent (one or more connection lines) and is surrounded on allsides, or at least on two sides, particularly in the linear extent, bylattice structures arranged loosely on each other. The punctiformconnection can thus comprise at least one connection point, inparticular several individual connection points each with an arealextent and/or at least one connection line, in particular severalindividual connection lines. A connection line can be formed fromseveral individual connection points arranged in a row, in particular inthe circumferential direction. The term connection point is not to beunderstood in the strict mathematical sense.

The punctiform connection can be arranged in the edge area, inparticular at the edge of a lattice structure. The edge area as a wholecan form the punctiform connection. The edge area forms an outer areawhich is arranged in the axial direction of the device and which isarranged at least outside the first intersection or the first cellsegment of the lattice structure. The outer area can, for example, bethe loop area of a braided stent. In a retractable braid with anobliquely tapering tip, as is described in DE 10 2009 056 450 or DE 102009 056 450, the content of each of which is fully incorporated byreference into this application, the area from the obliquely taperingtip to the in cross section cylindrically closed jacket area forms theedge area in which the lattice structures are connected. It is alsopossible to connect the lattice structures only at the oblique edge ofthe tip, for example by twisting the wires together.

If the punctiform connection is arranged at the edge of a latticestructure, the edge forms a limit of the connection. The other sides ofthe connection adjoin lattice structures arranged loosely on each other.Both lattice structures can each be connected at the edge, or onelattice structure at the edge and the other lattice structure away fromthe edge, for example in the middle area. This applies both to the firstand also the second lattice structure.

It is also possible that the at least one punctiform connection isarranged outside the lattice structure, for example by connectionstrands or filaments or wires that extend over the lattice structuresand are connected outside the lattice structures.

The punctiform connection can have different geometric shapes. Forexample, the shape of the connection can correspond to the shape of acell or of several contiguous cells. Generally, the punctiformconnection can be formed from individual subconnections, which for theirpart represent punctiform connections, for example in the form ofindividual wires or strands connected to each other at points. Thehigher-order punctiform connection is at least partially surrounded bylattice structures arranged loosely on each other, in such a way that,in the unconnected area of the lattice structures, a relative movementof the lattice structures is possible. This applies both to areal andalso to linear punctiform connections.

The linear connection can extend in the circumferential direction and/orin the longitudinal direction and/or obliquely with respect to thelongitudinal axis of the device. It preferably extends only in thecircumferential direction or only in the longitudinal direction.

The length of the linear connection is at most 30%, in particular atmost 25%, in particular at most 20%, in particular at most 15%, inparticular at most 10%, in particular at most 5%, in particular at most4%, in particular at most 3%, in particular at most 2%, in particular atmost 1% of the total length of the device in the longitudinal directionor of the circumference of the device.

It is possible that the punctiform connection is arranged at the edge oreven outside of the two lattice structures. For example, the two latticestructures can be connected by a common strand or guide wire by whichthe device can be actuated or can be moved in a delivery system. In thiscase, the two lattice structures are arranged loosely on each otheracross the entire surface area of the device and are fixed only at theaxial end, where the two lattice structures are connected to the strandor to the guide wire.

The two layers or lattice structures are arranged coaxially one insidethe other. This has the effect that the tubular body, in a compressedstate, has a smaller cross-sectional diameter than in the prior art.Specifically, the invention provides for a regular arrangement of theindividual wires or webs of the lattice structure, as a result of whichthe number of unused free spaces between the individual wires or webs isreduced. The crimpability or compressibility of the tubular body is thusincreased.

By virtue of the double-walled structure, or the multi-layered design ofthe circumferential wall composed of mutually movable layers, it ispossible to cover different application possibilities. Thus, in thedevice according to the invention, a division of functions can beprovided in which one of the lattice structures has, for example, acarrying or supporting function, and the other or a further latticestructure has the function of influencing the flow in the area of ananeurysm.

The lattice structures or separate layers are connected to each other atpoints. The punctiform connection between the lattice structures ensuresthat the lattice structures substantially maintain their positionrelative to each other. In particular, the lattice structures maintaintheir relative position independently of a compressed or expanded state.Parts or sections of the lattice structures are able to move relative toeach other. However, complete displacement of the two lattice structuresrelative to each other is prevented by the punctiform connection. Inthis way, the risk of dislocation of the medical device is minimized.

In a preferred embodiment of the medical device according to theinvention, the first lattice structure and/or the second latticestructure is formed in each case from interwoven wires. Preferably, bothlattice structures, or generally the lattice structures of thecircumferential wall, each have a wire braid. The individual wire braidsor lattice structures are therefore advantageously formed from severalwires which extend in a spiral shape about a longitudinal axis of thetubular body. Wire spirals are provided that run in opposite directionsand are interwoven. The individual layers of the circumferential wallare therefore formed by wire braids or interwoven wires or bands.However, the interweaving is present exclusively within an individuallayer. The individual layers are interconnected at points, such that arelative movement between the layers is permitted.

It will be noted in this connection that the application does not onlydisclose and claim lattice structures that comprise a wire braid.Instead, the invention also includes lattice structures that are formedon the basis of lattice webs. Lattice structures of this kind can beproduced, for example, by laser cutting or chemical vapor deposition.

In the context of the invention, provision is also made that eachindividual wire element of a lattice structure or of a layer comprises asingle site at which the wire or the wires is or are connected to a wireor to wires of an adjacent layer. This has the effect that a punctiformconnection exists between the layers.

The first lattice structure can have a proximal end, which is connectedto a proximal end of the second lattice structure in such a way thatdistal ends of the first and second lattice structures arranged oppositethe proximal ends are movable relative to each other. This embodimentgoes back to the idea of interconnecting the lattice structures of theseparate layers at in each case an axial end, in particular at theproximal ends. Thus, the entire lattice structure is movable betweenthese. By contrast, the distal ends of the first and second latticestructures are arranged free, such that the distal ends of the latticestructure are movable relative to each other. The relative mobility ofthe lattice structures at least in some sections has the particularadvantage of permitting a division of functions. In particular, thefirst and second lattice structures can have different geometries, suchthat different functions can be performed by the first and secondlattice structures. The connection of the proximal ends of the latticestructures to each other is particularly advantageous, since the areawhere the lattice structures are movable relative to each other is quitelarge. In this way, different properties of the lattice structures canbe combined across a relatively large area or the entire area of thetubular body. As an alternative to the connection of the proximal endsof the lattice structures, it is also possible that the distal ends ofthe first and second lattice structures are connected to each other.Moreover, the first and second lattice structures can be connected toeach other at points in a middle area of the tubular body. The free endsof the lattice structures at the distal and/or proximal end of thedevice have the effect that the two lattice structures can shortenindependently of each other during the expansion in the vessel(foreshortening), for example if the two lattice structures havedifferent braiding angles.

It generally applies that a division of functions of the two structuresis permitted by the only punctiform connection of the latticestructures.

According to another preferred embodiment, the first lattice structureand the second lattice structure, in a production state, have braidingangles that are the same at least in some sections or different from oneanother. Different braiding angles between the first lattice structureand the second lattice structure, or between the separate layers of thetubular body, have the effect that the lattice structures shorten todifferent extents during the expansion of the tubular body. Even in theevent of a change of cross section of the hollow organ of the body inwhich the medical device is inserted, the lattice structures withdifferent braiding angles behave differently. The different shorteningof the lattice structures can be used advantageously for precisepositioning of the medical device. For example, the second latticestructure can be designed in such a way that the effect of theforeshortening is reduced. The second lattice structure can therefore bepositioned relatively exactly. Since the first lattice structure isconnected to the second lattice structure at points, a precisepositioning of the second lattice structure at the same time permits arelatively precise positioning of the first lattice structure orgenerally of the tubular body.

Preferably, the braiding angle of the first lattice structure and/or ofthe second lattice structure is at most 70°, in particular at most 65°,in particular at most 60°, in particular at most 59°, in particular atmost 57°, in particular at most 55°, in particular at most 52°, inparticular at most 50°. Such a braiding angle on the one hand ensures asufficient flexibility of the lattice structures. On the other hand,such a braiding angle limits the foreshortening effect. Moreover,squashing together is reduced, such that the predetermined through-flowresistance is not impaired.

In a radially expanded state of the tubular body, a gap can be formed atleast in some sections between the first lattice structure and thesecond lattice structure. Particularly in conjunction with differentbraiding angles for the first lattice structure and the second latticestructure, this ensures that, in the event of a change of the crosssection or length of the hollow organ of the body in which the medicaldevice is arranged, the two lattice structures lift away from eachother. In this way, a gap is formed between the lattice structures, inparticular an annular gap.

For example, the gap can be produced if the outer, second latticestructure or the outer net has, in the longitudinal direction, twospaced-apart, punctiform connections to the inner lattice structure, forexample two connection lines extending in the circumferential direction,or individual connection points along two lines extending in thecircumferential direction. The connection lines can be arranged at theaxial ends of the lattice structure or can be offset axially inward fromone or both ends. The two lattice structures have different braidingangles. The outer, second lattice structure has a smaller braiding angleand, therefore, a smaller foreshortening than the inner, first latticestructure. In the expanded state, the inner lattice structure isshortened to a greater extent than the outer lattice structure. Thisleads to an outward bulging of the second lattice structure and,therefore, to a gap between the two lattice structures. The differencein braiding angle can be at least 1°, in particular at least 2°, atleast 3°, at least 4°, at least 5°, at least 10°, at least 15°, at least20°, at least 25°, at least 30°. The upper limit for the range of thedifference in braiding angle is at most 30°, in particular at most 25°,at most 20°, at most 15°, at most 10°, at most 5°, at most 4°, at most3°, at most 2°, at most 1°. The aforementioned upper and lower limitscan be combined with one another.

Generally, the bulge can occur between individual, axially spaced apartconnection points, in particular between pairs of axially spaced apartconnection points. It is possible to provide two longitudinally spacedapart connection lines composed of several connection points arranged inseries in the circumferential direction. It is also possible to providemore than two such connection lines, between each of which a bulge isformed, such that several bulges are arranged in succession.

Flow eddies, which form a kind of cushion, develop in the gap betweenthe lattice structures. The cushion leads to a desired loss of energy,such that the flow velocity is slowed down. The shear stresses in themain vessel thus act initially in the gap and generate the eddy there.The shear stresses transferred from the gap into the aneurysm via thewall of the net, or of the outer lattice structure, are thereby reduced.Clotting is promoted in the aneurysm. Moreover, the local pressure loadsacting on the aneurysm wall and caused by the inflow of blood into theaneurysm are reduced.

Preferably, the first lattice structure and the second lattice structureeach have closed meshes. The size of the meshes of the first latticestructure is advantageously different than the size of the meshes of thesecond lattice structure. In particular, the first lattice structure canhave a smaller mesh size than the second lattice structure. In otherwords, the first lattice structure preferably has a finer mesh than thesecond lattice structure. The second lattice structure can, for example,form a carrier structure for the net-like structure of the first latticestructure. In this way, the division of functions between the twolattice structures or layers of the circumferential wall is ensured. Thesecond lattice structure supports or fixes the first lattice structurein the blood vessel. By contrast, the first lattice structure can havesuch a fine mesh as to efficiently influence the flow of the blood intothe aneurysm. Moreover, the first lattice structure can be flexible insuch a way that the first lattice structure is easily able to follow achange of cross section of the blood vessel.

The wires of the first lattice structure preferably have a smallercross-sectional diameter than the wires of the second lattice structure.The expansibility of the first lattice structure compared to the secondlattice structure is thereby increased. Moreover, the first latticestructure can have a greater number of wires than the second latticestructure. This ensures that the first lattice structure has a finermesh than the second lattice structure. In connection with a smallercross-sectional diameter of the wires of the first lattice structure,the expansibility of the first lattice structure is further increased bycomparison with the second lattice structure. The function ofinfluencing the flow of blood into the aneurysm is improved.

Preferably, the first lattice structure forms an outer layer and thesecond lattice structure forms an inner layer of the tubular body. Thesecond lattice structure can form a carrier structure, and the firstlattice structure can form a net-like covering structure. The carrierstructure supports the covering structure from the inside. This avoids asituation where the first lattice structure or the covering structuredoes not completely deploy upon expansion. The inner carrier structure,or the second lattice structure forming the inner layer, supports thefirst lattice structure across the entire length thereof.

In another preferred embodiment of the medical device, the first latticestructure has an axial lengthwise extent that is smaller than an axiallengthwise extent of the second lattice structure, in such a way thatthe first lattice structure covers the second lattice structure in somesections, in particular by at most 98%, at most 97%, at most 96%, atmost 95%, at most 94%, at most 93%, at most 92%, at most 91%, at most90%, at most 85%, at most 80%, at most 75%, at most 70%, at most 65%, atmost 60%, at most 55%, at most 50%, at most 45%, at most 40%, at most35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, atmost 5%, relative to the longer lattice structure. The aforementionedgeometric ratios relate to the production state of the medical device.The production state corresponds substantially to an unloaded state.This means that the medical device is not exposed to an external forcecausing a compression of the tubular body. In other words, the tubularbody is fully expanded in the production state.

It is also possible to adapt the device such that the aforementionedgeometric ratios are present in the compressed state, wherein the firstlattice structure is shorter than the second lattice structure. Theaforementioned values are also disclosed in connection with thecompressed state.

The difference in length between the two lattice structures can beincreased, decreased or maintained constant upon expansion throughadaptation of the foreshortening by means of a suitable choice of thebraiding angles. For example, the difference in length can be shortenedby at least 10%, in particular at least 20%, in particular at least 30%,in particular at least 40%, in particular at least 50%, in particular atleast 60%, in particular at least 70%, in particular at least 80%, inparticular at least 90% or by 100% (length equalization). On the otherhand, the difference in length can be increased by at least 2%, inparticular at least 5%, in particular at least 10%, in particular atleast 20%, in particular at least 30%, in particular at least 40%, inparticular at least 50%, in particular at least 60%. At length equality,i.e. when the starting difference is 0 mm, the aforementioned valuesrelate to the total length of one of the two lattice structures.

In absolute values, the difference in length can be changed (decreasedor increased) as follows: 1 mm, 5 mm, 10 mm, 15 mm, 20 mm. In the caseof the decrease of the difference in length, these values are lowerlimits (at least) and in the case of the increase they are upper limits(at most).

Preferably, the second lattice structure is covered at least in somesections by the first lattice structure. The tubular body therefore hasat least one section that has a multi-layer design.

The tubular body can have at least a third lattice structure. The thirdlattice structure preferably forms, together with the first latticestructure, the outer layer of the tubular body or of the circumferentialwall of the tubular body. Generally, the individual separate layers ofthe circumferential wall can have several lattice structures. Thelattice structures of individual layers can be movable relative to eachother. It is important that independent layers each comprise at leastone lattice structure that is movable in some sections relative to alattice structure of an adjacent layer. It is preferable if the outerlayer has several lattice structures. In the compressed and/or expandedstate of the tubular body, the lattice structures of the outer layer,i.e. the first and third lattice structures, can be arranged flush witheach other. The cross-sectional diameter of the tubular body in thecompressed state is thus reduced. Alternatively, the lattice structuresof the outer layer, i.e. the first and third lattice structures, can bearranged overlapping in the compressed and/or expanded state of thetubular body. This allows the second lattice structure to be coveredover a relatively large surface area in an expanded state of the tubularbody.

Preferably, the first lattice structure is connected at a proximal end,and the third lattice structure at a distal end, to the second latticestructure which forms the inner layer of the tubular body. In otherwords, the first and third lattice structures each have an end fixed tothe second lattice structure and also a free end, wherein the free endsof the first and third lattice structures are arranged facing each otheror adjacent to each other. In the compressed state of the tubular body,the free ends of the first and third lattice structures can be arrangedflush with each other or in alignment. The free ends of the first andthird lattice structures can also overlap each other in the compressedstate of the tubular body.

Provision is preferably made that the first lattice structure and thethird lattice structure overlap at least in some sections in a radiallycompressed state or a radially expanded state. On account of theforeshortening effect, which acts not only on the first and thirdlattice structures, but in particular on the second lattice structurethat forms the inner layer of the tubular body, a shortening of theinner layer or second lattice structure takes place during the expansionof the tubular body. The two lattice structures that form the outerlayer, i.e. the first and third lattice structures, moves closer to eachother during the expansion of the tubular body. By suitable design ofthe individual lattice structures, it is possible to ensure that thefirst and third lattice structures overlap in some sections in theexpanded state of the tubular body. During the expansion, the free endsof the first and second lattice structures thus move closer to eachother and push over each other. This is the case when the effect of theforeshortening of the outer lattice structure is less than the effect ofthe foreshortening of the inner lattice structure. Preferably, theoverlapping area of the first and third lattice structures is arrangedat the treatment site in the area of the aneurysm. This has the effectthat the outer layer of the tubular body has an increased expansibilityin the area of the aneurysm, since the free ends of the first and thirdlattice structures are movable relative to each other. Under theinfluence of the blood flow, the free ends of the first and thirdlattice structures or of the overlap areas are therefore able to bulgeinto the aneurysm, such that a flow cushion is formed between the outerlayer and the inner layer or the second lattice structure in the area ofthe aneurysm, in which cushion the flow energy of the blood flowing intothe aneurysm is reduced and, consequently, the load applied to theaneurysm wall is minimized. It is also possible that the first and thirdlattice structures overlap each other in some sections both in theradially compressed state and also in the radially expanded state. Thelattice structures, or the inner layer and the outer layer, can bedesigned in such a way that the first and third lattice structures donot overlap in the radially expanded state of the tubular body. In otherwords, the free ends of the first and third lattice structures in theradially expanded state can be arranged flush on each other or spacedapart from each other. The first and third lattice structures can thusbe arranged in alignment with each other in the radially expanded stateof the tubular body.

In another preferred embodiment, provision is made that the firstlattice structure and the third lattice structure each comprise aproximal end, which is connected to the second lattice structure. Inthis case, the proximal end of the first lattice structure can bearranged at a distance from the proximal end of the second latticestructure. The outer layer can generally comprise several latticestructures which each form an axial section of the outer layer. Thelattice structures, in particular the first and third latticestructures, each have a proximal end which is connected at points to thesecond lattice structure, i.e. the inner layer. The distal end of thefirst and third lattice structures is arranged free. The first and thirdlattice structures can overlap each other. In this way, the first andthird lattice structures can form a scale-like outer layer. Inparticular, the first and third lattice structures can have a valvefunction, wherein the first and third lattice structures areadvantageously positioned in the area of an aneurysm. The free ends ofthe first and/or third lattice structures can be deflected radiallyoutward with respect to the inner layer of the tubular body, such that acatheter, for example a catheter for the positioning of coils, can beinserted into the aneurysm, wherein the catheter is guided through themeshes of the second lattice structure and deflects at least one freeend of the first or third lattice structure radially outward, in orderto gain access to the aneurysm.

In another preferred embodiment of the medical device, provision is madethat the first lattice structure comprises a middle section and two edgesections delimiting the middle section. In the middle section, the firstlattice structure has a smaller braiding angle than in the edgesections. Generally, provision can be made that the braiding angle ofthe respective lattice structure is variable. In other words, thebraiding angle can change along the lattice structure, particularly inthe longitudinal direction of the lattice structure. Preferably, thebraiding angle changes along the first lattice structure in such a waythat a smaller braiding angle is present in the middle section than inthe edge sections. This ensures that the first lattice structure in themiddle section has a greater radial expansibility compared to the edgesections. The middle section of the first lattice structure cantherefore be expanded in the radial direction further than the edgesections. The expansibility is a result of the local flexibility in themiddle section. However, the term flexibility is used primarily for thebending behavior of the whole device or of the whole stent.

An elongation of the vessel section in which the medical device isinserted is compensated by the edge sections during the systole. It isthus ensured that the axial ends of the first lattice structure, inparticular a free end of the first lattice structure, do notsignificantly change their position. The positioning of the firstlattice structure is instead maintained. By contrast, the middle sectionwith the smaller braiding angle can utilize the smaller foreshorteningeffect during the systole. Specifically, the middle section of the firstlattice structure can shorten during an elongation and simultaneouswidening of the vessel section. Preferably, the middle section ispositioned at the level of the aneurysm or of the aneurysm neck. Thisensures that the middle section of the first lattice structure can bulgeinto the aneurysm or into the area of the aneurysm neck during thesystole. As a result of the small braiding angle, the change in lengthis not significant. Thus, the middle section of the first latticestructure contributes to transferring the systolic pressure from theblood vessel into the aneurysm at least to a certain degree, such thatthe cells of the aneurysm wall are still under a mechanical load.Degeneration of the cells in the aneurysm wall is thus avoided.

In a preferred embodiment, the distance between the outer layer and theinner layer varies in the expanded state of the body, wherein thedistance alternately decreases and increases at least in some sections.Specifically, the outer layer, in the expanded state of the body, has anundulating contour at least in some sections. The undulating contour isparticularly effective in slowing down the flow.

The outer layer can have alternately disposed peaks and valleys, whereinat least some, in particular all, of the valleys are connected to theinner layer and/or are preshaped, in particular preshaped by heattreatment, and/or have another braiding angle than the peaks. In theconnection, particularly the mechanical connection, of the valleys tothe inner layer, it can be advantageous to connect a single valley ormore than 1 valley, in particular more than 2 valleys, more than 3valleys, more than 4 valleys, in particular all the valleys, to theinner layer and fix them. The fixed valleys are arranged proximally,i.e. on the same side as the proximal end of the outer layer. The distalend of the outer layer, and any unfixed valleys on the distal side, aremovable in the axial direction. In a particularly preferred embodiment,only the proximal end is fixed which can be seen as a half valleyproximally from the first peak. All complete valleys including thedistal end are free and movable.

The undulating shape can be preshaped by mechanical forming or can beembossed and forms the rest state. In the catheter line, the undulatingshape is stretched out and, upon release, it returns to the undulatingrest state or starting state. When using a shape-memory material, theundulating shape can be embossed by a suitable heat treatment, utilizingthe shape-memory effect. By means of different braiding angles, theradial stability can be locally influenced, such that some areas wideneasily (peaks) and some areas widen less easily (valleys). Theaforementioned options for utilizing the undulating contour can be usedsingly or in combination.

According to a subsidiary aspect, the invention is based on the conceptof making available a system for medical uses, with a device as claimedin claim 1, and with a delivery system which comprises a flexibledelivery element, in particular a guide wire. The delivery element isconnected or connectable to the device. The system is preferably adaptedin such a way that the device can be drawn back into the deliverysystem.

The illustrative embodiments and advantages that have been described inconnection with the medical device apply equally to the system havingsuch a device.

The invention is explained in more detail below on the basis ofillustrative embodiments and with reference to the attached schematicdrawings, in which:

FIG. 1 a shows a cross section through a blood vessel with an aneurysmand indicates the transfer of pressure into the aneurysm;

FIG. 1 b shows the blood vessel according to FIG. 1 a, with aconventional aneurysm stent inserted;

FIG. 1 c shows a graph illustrating the pressure profile in the bloodvessel and in the aneurysm when a conventional aneurysm stent isinserted;

FIG. 2 a shows a cross section through a blood vessel with an aneurysmand indicates the influence of the shear stress on the aneurysm;

FIG. 2 b shows the blood vessel according to FIG. 2 a, with aconventional aneurysm stent inserted;

FIG. 3 a shows a cross section through a blood vessel with an aneurysmand indicates the influence of a direct flow of blood into the aneurysm;

FIG. 3 b shows the blood vessel according to FIG. 3 a, with insertion ofa conventional aneurysm stent having a small mesh size;

FIG. 3 c shows the blood vessel according to FIG. 3 a, with insertion ofa conventional aneurysm stent having a large mesh size;

FIG. 4 a shows a longitudinal section through a blood vessel, with ananeurysm and with an inserted conventional aneurysm stent, and indicatesthe influence that pulse-induced changes in the blood vessel have on theaneurysm stent;

FIG. 4 b shows the blood vessel according to FIG. 4 a and indicates anincreased flow of blood into the aneurysm through the meshes of aconventional aneurysm stent, under the influence of a systolic bloodpressure;

FIG. 5 a shows a longitudinal section through a blood vessel with ananeurysm, and with insertion of a conventional aneurysm stent having alarge braiding angle;

FIG. 5 b shows the blood vessel according to FIG. 5 a, with insertion ofa conventional aneurysm stent having a small braiding angle;

FIG. 6 a shows a cross section through an aneurysm stent according tothe prior art in a delivery system, wherein the aneurysm stent has aplurality of interwoven wall layers;

FIG. 6 b shows a cross section through a medical device according to theinvention, in a preferred illustrative embodiment, in a delivery system,wherein the device has two separate layers of lattice structures;

FIG. 7 shows a longitudinal section through a blood vessel with ananeurysm, wherein a medical device according to the invention, in apreferred illustrative embodiment, is inserted which comprises a firstlattice structure with variable braiding angles;

FIG. 8 shows a perspective side view of a medical device in anotherillustrative embodiment according to the invention;

FIG. 9 shows the medical device according to FIG. 8 during release froma delivery system;

FIG. 10 shows the medical device according to FIG. 8 in an arrangementinside a blood vessel;

FIG. 11 shows the medical device according to FIG. 10 under theinfluence of an elongation of the blood vessel;

FIG. 12 shows the medical device according to FIG. 10 under theinfluence of a systolic blood pressure;

FIG. 13 shows a perspective side view of a medical device in anotherillustrative embodiment according to the invention, under the influenceof an elongation of the blood vessel, wherein an outer layer of thecircumferential wall comprises a shorter lattice structure than an innerlayer;

FIG. 14 shows a perspective side view of a medical device in anotherillustrative embodiment according to the invention, under the influenceof an elongation of the blood vessel, wherein the outer layer of thecircumferential wall comprises two lattice structures arranged insuccession;

FIG. 15 a shows a perspective side view of a medical device in anotherillustrative embodiment according to the invention in the implantedstate, wherein the outer layer of the circumferential wall comprises twolattice structures overlapping each other in the expanded state of thedevice;

FIG. 15 b shows the device according to FIG. 15 a in a compressed stateinside a delivery system;

FIG. 16 a shows a perspective side view of a medical device in anotherillustrative embodiment according to the invention, wherein the outerlayer of the circumferential wall comprises two lattice structuresarranged in alignment in the expanded state of the device;

FIG. 16 b shows the device according to FIG. 16 a in a compressed stateinside a delivery system;

FIG. 17 shows the device according to FIG. 12, wherein the reducededdying in the aneurysm is indicated by a cushion area between the firstand second lattice structures of the tubular wall;

FIG. 18 shows the developed view of a device in an illustrativeembodiment according to the invention in which two lattice structuresare superposed;

FIG. 19 shows a cross section through the device according to FIG. 18 inthe area of the connecting sleeve;

FIG. 20 shows a developed view of a carrier for a device in a furtherillustrative embodiment according to the invention;

FIG. 21 shows the developed view of a device in an illustrativeembodiment according to the invention, with the carrier according toFIG. 20;

FIG. 22 shows a perspective side view of a medical device in anillustrative embodiment according to the invention that is used to treata fusiform aneurysm;

FIG. 23 shows a perspective side view of a medical device in a furtherillustrative embodiment according to the invention that is used to treata fusiform aneurysm; and

FIG. 24 shows a perspective side view of a medical device in anotherillustrative embodiment according to the invention that is used to treata fusiform aneurysm.

In FIG. 1 a, the influence of the blood pressure on an aneurysm 31 in ablood vessel 30 is illustrated. The arrows show the transfer of thepressure P from the blood vessel 30 into the aneurysm 31. In general,the blood vessel 30 is subject to pressure fluctuations that aregenerated by the pulsatile blood flow or the pulsating activity of theheart. The pressure peaks occur during the so-called systole, i.e. theejection phase of the heart activity. The pressure is at a minimum inthe diastole, when the heart chambers fill with blood.

In the prior art, the influence of the pressure fluctuations on theaneurysm 31 is affected by the use of a conventional fine-meshedaneurysm stent 40. For this purpose, the conventional aneurysm stent 40is implanted in the area of the aneurysm 31 in the blood vessel 30 (FIG.1 b). The flow of blood between the blood vessel 30 and the aneurysm 31is influenced by the structure of the conventional aneurysm stent 40,such that the pressure P transferred into the aneurysm is on the onehand reduced and on the other hand acts on the aneurysm 31 with a timelag. FIG. 1 c provides an illustration of the pressure profile in theblood vessel 30 (solid line) and in the aneurysm 31 (broken line) ascovered by a conventional aneurysm stent 40. It can be seen clearly fromthe illustrated pressure profiles that the pressure in the aneurysm 31rises and falls more slowly than in the blood vessel 30. The pressurecurve in the aneurysm 31 is therefore flatter as a whole. The effect isall the more distinct the finer the mesh of the braid. The attenuationof the pressure is desirable but should not be too pronounced.

However, there is the possibility of the pressure reduction promoting adegeneration of the cells of the aneurysm wall 34. Particularly as aresult of the reduced mechanical stress of the aneurysm wall 34, thereis the danger of the cells of the aneurysm wall degenerating or breakingdown, thereby increasing the danger of a rupture even after insertion ofan aneurysm stent 40.

An aneurysm 31 is also influenced by the tangential blood flow or vesselflow F_(G), as is illustrated in FIG. 2 a. The vessel flow F_(G) resultsin shear stresses occurring at the interfaces between the blood insidethe aneurysm 31 and the blood inside the blood vessel 30, which leads toan eddy flow F_(W) inside the aneurysm 31. The influence of the shearstress triggered by the vessel flow F_(G) is reduced by the use of aconventional aneurysm stent 40, as is shown in FIG. 2 b. The eddy flowF_(W) inside the aneurysm 31 is thereby reduced. The reduction in theeddy flow F_(W) has on the one hand the advantage that clotting in theaneurysm is improved. On the other hand, however, an excessive reductionof the eddy flow F_(W) can promote the degeneration of cells of theaneurysm wall 34. Moreover, an exchange of blood between the blood inthe aneurysm 31 and the blood vessel 30 is impeded, with the result thatthe aneurysm wall 34 is in some cases insufficiently supplied withnutrients. Too great a reduction of the flow can lead to the formationof clots that grow too rapidly.

FIG. 3 a shows the influence of the vessel flow F_(G) on an aneurysm 31in the untreated state, when the aneurysm 31 is arranged in a curvatureof the blood vessel 30. The aneurysm 31 is in this case affecteddirectly by the vessel flow F_(G), since the vessel flow F_(G) impingeslocally on the aneurysm wall 34 in an attack region 36. The vessel flowF_(G) is deflected in the attack region 36. The aneurysm wall 34 isexposed to an increased pressure load in the attack region 36. Aconventional aneurysm stent 40 inserted into the blood vessel 30 offersa resistance to the vessel flow F_(G), such that the flow fraction orblood fraction that flows into the aneurysm 31 is reduced. Thus, aconventional aneurysm stent 40 causes a reduction of the flow velocityinto the aneurysm. Specifically, a through-flow F_(D) through theaneurysm neck 32 of the aneurysm is reduced. At the same time, theresistance that the conventional aneurysm stent 40 offers to the bloodflow or vessel flow F_(G) brings about a change of the pressure wave orof the pressure profile within the aneurysm, thereby promoting thedegeneration of the cells of the aneurysm wall 34. This applies inparticular to stents with a fine-meshed structure, which additionallyhave a high degree of bendability and therefore fit well into thecurvature of the blood vessel 30 (FIG. 3 b). By contrast, conventionalaneurysm stents 40 with a wide-meshed structure have a higher radialforce, which has the effect that the blood vessel 30 stretches, as isshown in FIG. 3 c. The elongation of the blood vessel 30 has the effectof reducing the fraction of the vessel flow F_(G) conveyed directly intothe aneurysm 31. However, the wide-meshed structure of known stents 40of this type permits at the same time a large flow of blood into theaneurysm 31, particularly as a consequence of shear stresses, such thatthe aneurysm is under a considerable load.

Conventional aneurysm stents 40, in particular conventional aneurysmstents 40 with a fine-meshed structure, are additionally influenced bythe periodic vascular changes of the blood vessel 30. FIG. 4 a showsthat during the systole, i.e. during a pressure peak in the profile ofthe blood pressure, the blood vessel 30 on the one hand experiencesradial expansion, i.e. has a widening W, and on the other hand isstretched in the longitudinal direction. In addition to the widening W,an elongation E of the blood vessel 30 also takes place during thesystole. On account of the foreshortening effect explained at theoutset, the widening W and elongation E of the blood vessel 30 cause anarrowing R of the conventional aneurysm stent 40. The narrowing R isseen in particular in the area of the aneurysm 31. As a result, thecircumferential wall of the conventional aneurysm stent 40 moves awayfrom the aneurysm neck 32, as is shown in FIG. 4 a. The considerabledanger of dislocation of the conventional aneurysm stent 40 isheightened by the widening of the vessels and the narrowing R. Moreover,the influence on the eddy flow F_(W) is reduced in the area of theaneurysm 31. The effectiveness of the treatment of the aneurysm 31 istherefore diminished. Specifically, the structure of conventionalaneurysm stents 40 shows substantially an inverse reaction during thesystole. Whereas the blood pressure assumes a maximum locally in thesystole, at the same time the aneurysm stent 40 narrows. In other words,the circumferential wall of the conventional aneurysm stent 40 movesagainst the rise in pressure. In this way, the through-flow F_(D)through the meshes of the conventional aneurysm stent 40 into theaneurysm 31 is increased. This effect is illustrated in FIG. 4 b.

Conventional aneurysm stents 40 with a large braiding angle, as shown inFIG. 5 a, are known from the prior art. Conventional aneurysm stents 40with a large braiding angle have the property of being able to follow anelongation E of the blood vessel, without experiencing severe narrowingR. As a whole, the structure of aneurysm stents 40 of this kind isrelatively dimensionally stable in the radial direction (lowcompliance), such that they additionally have a strong influence on thetransfer of pressure from the blood vessel 30 into the aneurysm 31. Thepressure P in the aneurysm 31 is reduced as a whole, as is shown in FIG.1 c.

FIG. 5 b shows a conventional aneurysm stent 40 that has a smallbraiding angle. Known stents of this kind have increased flexibility,but this means that a narrowing R of the conventional aneurysm stent 40occurs in the event of an elongation E of the blood vessel 30, with thedisadvantages described above.

FIG. 6 a shows a cross-sectional view of the known aneurysm stent 40according to DE 601 28 588 T2 in the compressed state inside a deliverysystem 20. The known aneurysm stent 40 has two layers of wire braids,wherein the wire braids of the two layers are interwoven. A first wirebraid has first wires 41, which have a larger cross-sectional diameterthan second wires 42 of a second layer of the conventional aneurysmstent 40. The interweaving of the first and second wires 41, 42 meansthat, in the compressed state inside the delivery system 20, the firstand second wires 41, 42 are in a complex arrangement and need a largeamount of space in the compressed state.

By contrast, in the illustrative embodiment according to the invention,provision is made that the medical device comprises a tubular body 10.The device is designed in particular as a stent. The tubular body 10 hasa circumferential wall, which comprises a first lattice structure 11 anda second lattice structure 12. The first and second lattice structures11, 12 each form separate layers 14, 15 of the circumferential wall. Thelattice structures 11, 12 of the tubular body 10 according to theinvention are therefore independent of each other at least in somesections, preferably along the whole of the lattice structure. Thelattice structures 11, 12 are connected to each other at points. Inparticular, the circumferential wall of the tubular body can comprise acircumferential line in which the first lattice structure 11 isconnected to the second lattice structure 12. In particular, a singleconnecting line between the first lattice structure 11 and the secondlattice structure 12 can be provided which extends in thecircumferential direction about the tubular body 10. It is explicitlynoted that the connection between the first lattice structure 11 and thesecond lattice structure 12, and possibly further lattice structures,does not take place across an extensive surface area but insteadsubstantially in a line shape.

As a result of the separate layers that each comprise a latticestructure 11, 12, the space taken up by the tubular body 10 in thecompressed state is reduced, as is shown in FIG. 6 b. FIG. 6 b shows across section through the tubular body 10 which, in the expanded state,comprises two layers 14, 15 that are arranged in the shape of a hollowcylinder (see FIG. 12 for example) and that each have a latticestructure 11, 12. An inner layer 15 is provided, which has the secondlattice structure 12. An outer layer 14, which surrounds the inner layer15, comprises the first lattice structure 11. The layered and concentricarrangement of the two lattice structures 11, 12 is maintained in thecompressed state, as is illustrated in FIG. 6 b.

The wires 112 of the first, outer lattice structure 11 have across-sectional diameter that is smaller than the cross-sectionaldiameter of the wires 122 of the second, inner lattice structure 12. Thetubular body according to FIG. 6 b is arranged inside a delivery system20. As a result of the reduced space taken up by the tubular body 10compared to conventional aneurysm stents 40, it is possible to use asmaller delivery system 20. The medical device can therefore beintroduced into smaller blood vessels.

It will also be seen from FIG. 6 b that the first lattice structure 11and the second lattice structure are arranged coaxially one inside theother. The first lattice structure 11 and the second lattice structure12 are also movable relative to each other at least in some sections.Specifically, the first and second lattice structures 11, 12 are movablerelative to each other outside the linear or punctiform connectionbetween the first and second lattice structures 11, 12. The relativemobility applies in particular to the individual wires 112, 122 of thefirst and second lattice structures 11, 12. In particular, the wires 112of the first lattice structure 11 can slide on the wires 122 of thesecond lattice structure 12, and vice versa.

In the illustrative embodiment according to the invention shown in FIG.6 b, the wires 112 of the first lattice structure 11 are thicker thanthe wires 122 of the second lattice structure 12. It is also possiblethat the wires 112, 122 of the lattice structures 11, 12 have the samecross-sectional diameter. Moreover, the wires 122 of the second latticestructure 12 can have a larger cross-sectional diameter than the wires112 of the first lattice structure 11. For the improved crimpability ofthe tubular body 10, or of the device generally, it is advantageous ifthe inner layer 15 is composed of a relatively smaller number of thickerwires 122 and the outer layer 14 is formed by a comparatively greaternumber of thinner wires.

In general, it has proven advantageous if one layer 14, has a finer meshstructure than the other layer 15, 14. In other words, one of the twolayers 14, 15 can comprise more wires 112, 122 than another layer 14,15. The wires 112, 122 can in this case be thinner than the wires 112,122 of the other layer 15, 14. It is possible that the more finelymeshed layer 14, 15 has a larger or a smaller braiding angle than thecomparatively wide-meshed layer 15, 14. Combinations of theaforementioned variants are possible.

It is particularly preferable if the fine-meshed layer is the outerlayer 14 and the wide-meshed layer is the inner layer 15.

Generally, the device preferably has a tubular body 10 comprising anouter layer 14 and an inner layer 15. The device can be a stent. Theouter layer 14 is formed by the first lattice structure 11 and the innerlayer 15 is formed by the second lattice structure 12. The secondlattice structure 12 preferably has a wide-meshed wire braid. Bycontrast, the first lattice structure 11 has a fine-meshed wire braid.The wide-meshed wire braid of the second lattice structure 12 thus formsa carrier 18, whereas the fine-meshed wire braid of the first latticestructure 11 forms a net 19.

Generally, it is possible that both layers, that is to say the outerlayer 14 and the inner layer 15, are designed alike. The layers 14, 15can thus have the same fine-meshed structure and/or the same number ofwires and/or the same wire thickness and/or the same braiding angles.All combinations of the aforementioned variants are possible. Theconnection of the lattice structures means that they are orientedrelative to each other or have braiding patterns oriented relative toeach other.

It will further be noted that the invention is not limited to structureshaving two layers. Instead, the scope of the application also claims anddiscloses tubular bodies 10 or stents that comprise a circumferentialwall with three or more separate layers. Some or all of the layers canbe constructed according to the invention.

Particularly advantageous configurations of the carrier 18 are describedbelow:

The carrier 18 or the second lattice structure 12 preferably has at most32 wires 122, in particular at most 24, in particular at most 20, inparticular at most 16, in particular at most 12, in particular at most8, in particular at most 6. The wires 122 of the second latticestructure 12 or of the carrier 18 preferably have a cross-sectionaldiameter of at least 40 μm, in particular at least 50 μm, in particularat least 60 μm, in particular at least 68 μm, in particular at least 75μm, in particular at least 84 μm, in particular at least 100 μm. Thisapplies to medical devices for use in blood vessels 30 that have across-sectional diameter of 2 mm to 6 mm. If the blood vessel 30 to betreated has a cross-sectional diameter of greater than 6 mm, the wires122 of the second lattice structure 12 or of the carrier 18 preferablyhave a cross-sectional diameter of at least 40 μm, in particular atleast 50 μm, in particular at least 60 μm, in particular at least 68 μm,in particular at least 75 μm, in particular at least 84 μm, inparticular at least 100 μm, in particular at least 150 μm, in particularat least 200 μm.

In principle, the circumferential wall of the tubular body 10 cancomprise more than one carrier 18.

Generally, the carrier 18 or the second lattice structure 12 has a highdegree of bendability, and the bending of the second lattice structure12 or of the carrier 18 along a longitudinal axis of the second latticestructure 12 requires a relatively high bending force or a relativelyhigh bending moment. This means that the carrier 18 causes an elongationof a curved blood vessel 30. The carrier 18 thus contributes to reducingthe flow component of vessel flow F_(G) flowing directly into theaneurysm 31. The direct inflow of the vessel flow F_(G) into theaneurysm 31 is thus reduced.

The carrier 18 can in the widest sense be a supporting structure orcarrying structure for the net 19. It is preferable that the carrier 18is arranged coaxially inside the net 19. In this way, the carrier 18 orthe second lattice structure 12 can be used to stabilize the net 19 orthe first lattice structure 11. In particular, the expansion behavior ofthe net 19 can be controlled by the carrier 18.

The carrier 18 preferably forms the inner layer 15 of the tubular body10. Alternatively, the carrier 18 can form the outer layer 14. In thisway, the carrier 18 permits good stabilization of the blood vessel 30and an expansion of the tubular body 10 up to a pre-definedcross-sectional diameter. Overall, the carrier 18 permits good andcontrollable expansion of the tubular body 10 and of the net inside thecarrier 18.

Preferred variants of the net 19 or of the first lattice structure 11are described below:

The net 19 preferably has finer meshes than the carrier 18. Thus, thenet 19 mainly has the function of influencing the flow in relation tothe aneurysm 31.

The fine-meshed structure of the net 19 is preferably limited to theextent that flow of blood into the aneurysm 31 is not completelyprevented. Instead, the net 19 is intended, on the one hand, to preventa rupture of the aneurysm 31 and, on the other hand, to maintainsufficient nutrient supply and mechanical loading of the aneurysm wall34, such that a degeneration of the cells of the aneurysm wall 34 isavoided. As regards the fine-meshed nature of the net 19, it istherefore advantageous if the net 19 has at most 48 wires 112, inparticular at most 44, in particular at most 40, in particular at most36, in particular at most 32, in particular at most 24, in particular atmost 20, in particular at most 16, in particular at most 12. The net 19is stabilized by the carrier 18, such that the net 19 does not have tomeet any particular requirements as regards the radial force. In orderto improve the crimpability, provision is therefore advantageously madeto reduce the wire diameter of the wires 112 of the first latticestructure 11 or of the net 19 in relation to the cross-sectionaldiameter of the wires 122 of the second lattice structure 12 or of thecarrier 18. Preferably, the wires 112 of the first lattice structure 11or of the net 19 have a cross-sectional diameter of at most 77 μm, inparticular at most 51 μm, in particular at most 46 μm, in particular atmost 41 μm, in particular at most 36 μm, in particular at most 26 μm, inparticular at most 20 μm. This applies to the use of the tubular body10, or generally of the medical device, in blood vessels 30 that have avessel diameter of 2 mm to 6 mm. If the vessel has a diameter of greaterthan 6 mm, it is advantageous if the wires 112 of the first latticestructure 11 or of the net 19 have a cross-sectional diameter of at most155 μm, in particular at most 105 μm, in particular at most 77 μm, inparticular at most 51 μm, in particular at most 46 μm, in particular atmost 41 μm, in particular at most 36 μm, in particular at most 26 μm, inparticular at most 20 μm.

The net 19 preferably forms the outer layer 14 of the tubular body 10.The highly flexible net 19 is supported by the carrier 18 during theexpansion of the tubular body 10 and forced into the expanded state. Theinteraction between carrier 18 and net 19 prevents a situation where thenet 19 does not deploy sufficiently in the blood vessel 30. The carrier18 forming the inner layer 15 preferably supports the net 19 along theentire length of the net 19.

The first lattice structure 11 and the second lattice structure 12 areconnected to each other at points. The connection of the first latticestructure 11 to the second lattice structure 12 preferably takes placeat a proximal end of the tubular body 10. In particular, the firstlattice structure 11 has a proximal end 110, which is connected to aproximal end 120 of the second lattice structure 12.

It will be noted here that, in the context of the application, proximalelements are arranged closer to the user than distal elements.

The first lattice structure 11 and the second lattice structure 12preferably each have an obliquely tapering proximal end 110, 120. Thewires 112, 122 of the first lattice structure 11 and of the secondlattice structure 12 converge at the obliquely arranged proximal ends110, 120. The converging wires 112, 122 are connected to each other.Such a connection of the first and second lattice structures 11, 12 isshown by way of example in FIG. 8. According to the illustrativeembodiment in FIG. 8, the connection of the converging wires 112, 122 ofthe first lattice structure 11 and of the second lattice structure 12 iseffected by a connecting sleeve 17. The converging wires 112, 122 of thefirst and second lattice structures 11, 12 can run parallel to eachother in the area of the connecting sleeve 17 or can be twistedtogether. Moreover, provision can be made that the wires 112 of thefirst lattice structure 11 completely enclose the wires 122 of thesecond lattice structure in the area of the connecting sleeve 17. Thiscorresponds substantially to the arrangement as shown in thecross-sectional view according to FIG. 6 b. Conversely, it is alsopossible that the wires 122 of the second lattice structure 12completely enclose the wires 112 of the first lattice structure 11 inthe area of the connecting sleeve 17. Other types of connection arepossible. For example, the first lattice structure 11 and the secondlattice structure 12, or the net 19 and the carrier 18, can be connectedto each other in a middle area of the tubular body 17. Moreover, aconnection between the first and second lattice structures 11, 12,between net 19 and carrier 18, at a distal end of the tubular body 10 isconceivable, e.g. at the loops of the lattice structure. A connection inthe oblique area is possible.

Preferably, the lattice structures 11, 12 have a wire braid that has anoblique profile at a proximal end 110, 120 or generally at an axial endof the respective lattice structure 11, 12. Such wire braids aredescribed in the later published German patent application No. 10 2009056 450, which was filed by the applicant and which by reference isincorporated in full into the present application.

In order to achieve the dual function according to the invention, namelythat of sufficiently fixing the tubular body 10 or stent in the bloodvessel 30, and that of deliberately influencing the flow into ananeurysm 31 without promoting a degeneration of the muscle cells of theaneurysm wall 34, it is expedient to deliberately adjust the braidingangles of the individual wire braids or lattice structures 11, 12.Preferred illustrative embodiments for different braiding angles aredescribed below:

In conventional aneurysm stents 40, provision is made to choose thebraiding angle to be as large as possible, so that the aneurysm neck 32is closed as far as possible. The disadvantage of such treatmentpossibilities lies in an increased risk of bleeding, as a result ofdegeneration of the cells of the aneurysm wall and the formation ofincreasingly large fresh clots, a high degree of foreshortening, whichmakes positioning of the conventional aneurysm stents 40 difficult, andan insufficient adaptation to variable vessel diameters. It generallyapplies that, upon a change of diameter, the change of length of aconventional aneurysm stent is all the greater, the larger the chosenbraiding angle. This makes a reproducible and adjustable configurationof known aneurysm stents 40 difficult.

Therefore, in the medical device, provision is advantageously made forthe braiding angle to be limited. In particular, it has proven expedientif the braiding angle is at most 70°, in particular at most 67°, inparticular at most 65°, in particular at most 63°, in particular at most60°. The braiding angle relates to the acute angle that is formedbetween a wire of the lattice structure and the longitudinal axis of thetubular body 10. It was found that with a braiding angle of 60°, ashortening of the respective lattice structure 11, 12 during expansion,i.e. during the transfer of the tubular body 10 from a compressed stateto an expanded state, amounts to 50%. This means that the latticestructure 11, 12 with a braiding angle of 60°, which has a length of 40mm in the compressed state, i.e. inside the delivery system 20, has alength of 20 mm or slightly over 20 mm in the expanded state,particularly in the blood vessel 30.

Preferably, a braiding angle for the first lattice structure 11 or thesecond lattice structure 12 is provided which is at most 60°, inparticular at most 59°, in particular at most 58°, in particular at most57°, in particular at most 56°, in particular at most 55°, in particularat most 54°, in particular at most 53°, in particular at most 52°, inparticular at most 51°, in particular at most 50°, in particular at most45°. This has the effect that the shortening of the tubular body 10,during the expansion or the release into a blood vessel 30, varieswithin an acceptable range. The foreshortening effect is therebyreduced. Since the tubular body 10 is usually overdimensioned, that isto say has a larger cross-sectional diameter in the production statethan in the implanted state within the blood vessel 30, the respectivelattice structure 11, 12 in the blood vessel 30 has a braiding angle ofapproximately 30° to 50°, such that the tubular body 10 hascomparatively good flexibility.

In this connection, it will be noted that the dimensions specified forthe medical device, in particular for the tubular body 10, in thecontext of the application relate in principle to the production state,unless indicated otherwise.

The first lattice structure 11 and the second lattice structure 12, orthe net 19 and the carrier 18, can have different braiding angles. Thismeans that different foreshortening effects arise during the expansionof the tubular body 10. In other words, upon release of the tubular body10 from a delivery system 20, the carrier 18 and the net 19, which havedifferent braiding angles, exhibit a different foreshortening behavior.This also applies in the implanted state when blood pressurefluctuations resulting from the pulsatile blood flow act on the tubularbody 10. The two layers 14, 15, i.e. the carrier 18 and the net 19, aretherefore influenced differently by the pulsatile blood flow. In aparticularly preferred manner, provision can be made that a gap 16 formsbetween the carrier 18 and the net 19, or between the outer layer 14 andthe inner layer 15, in particular between the first lattice structure 11and the second lattice structure 12. The gap 16 can act as a cushion.The gap can be obtained, for example, when the braids are connected in apunctiform manner in one area and have different braiding angles in atleast one area. The braiding angle can vary along the longitudinal axis.

In a preferred variant, the braiding angle of the carrier 18 is smallerthan the braiding angle of the net 19. This means that, upon releasefrom a delivery system, the net 19 shortens to a greater extent than thecarrier 18. In this way, the positioning of the tubular body 10 as awhole can be simplified, since the carrier 18 exhibits a minorforeshortening effect during the expansion. Generally, the tubular body10 is released from a delivery system 20, when the delivery system withthe compressed tubular body 10 has been guided to the treatment site.The delivery system 20 is then pulled in the proximal direction, whereasthe tubular body 10 is kept fixed in position. In order to compensatefor the foreshortening, provision can be made for a proximal end of thetubular body 10 to be pushed slightly in the distal directionsimultaneously with the proximal movement of the delivery system 20.This ensures that the outer layer 14 of the tubular body 10 is notpulled along the vessel wall 35 of the blood vessel 30 and does notdamage the vessel wall 35. The fact that the carrier 18 has a smallerbraiding angle than the net 19 means that, during the expansion of thetubular body 10, the proximal end 120 of the second lattice structure 12or of the carrier 18 has to be pushed only a short distance in thedistal direction against the foreshortening. This therefore facilitatesthe positioning of the tubular body 10 or of the multi-layer stent. Bycontrast, the net 19 or the first lattice structure 11 experiencesgreater shortening, as a result of which the fine mesh of the net 19increases during the expansion. In this way, a very considerably finemesh can be achieved using an overall smaller number of wires 112, 122.

Moreover, the outer element, or the outer lattice structure, can have asmaller foreshortening than the inner element, or the inner latticestructure, such that the outer element bears well on the vessel wall.

FIG. 9 shows the release of the tubular body 10 from a delivery system20 into a blood vessel 30. Upon release of a distal end of the tubularbody 10, the distal end 115 of the first lattice structure 11 and thedistal end 125 of the second lattice structure 12 first of all deploysimultaneously and at the same height. When the delivery system 20 ispulled farther back in the proximal direction, a relative movement takesplace between the first lattice structure 11 and the second latticestructure 12, since, with further release of the tubular body 10, theforeshortening effect of the first lattice structure 11 is morepronounced than in the second lattice structure 12. A proximaldisplacement of the net 19 with respect to the carrier 18 thus takesplace. This proximal displacement of the net 19 with respect to thecarrier 18 is caused by the larger braiding angle of the net 19.Preferably, the net 19 is arranged on the outside of the carrier 18. Thenet 19 thus forms the outer layer 14 of the circumferential wall of thetubular body 10. By contrast, the carrier 18 forms the inner layer 15 ofthe circumferential wall. Alternatively, provision can be made that thenet 19 forms the inner layer 15 and the carrier 18 forms the outer layer14. This has the advantage that the net 19 can slide on wires 122 of thecarrier 8 during the expansion. The net 19 arranged on the outside has asmaller braiding angle than the carrier 18, and therefore also a smallerforeshortening effect then the carrier 18.

When the net in the preferred embodiment forms the outer layer 14, thecontact between the tubular body 10 and the vessel wall 35 of the bloodvessel 30 is established initially by the net 19. To compensate for theslight foreshortening of the carrier 18, the lattice structures 11, 12,or the proximal end of the tubular body 10, are pushed in the distaldirection. The inner carrier 18, or the inner layer 15, thus moves inthe distal direction. The carrier 18 can slide along the vessel wall 35.Since the carrier 18 has a relatively small braiding angle, it ispossible to push the carrier 18 along the vessel wall 35, without thecarrier 18 or the second lattice structure 12 being squashed together.With the comparatively small braiding angle of the carrier 18, the wires22 of the second lattice structure 12, or of the carrier 18, have adirectional component which is particularly pronounced in thelongitudinal direction, that is to say parallel to the longitudinalaxis, of the tubular body 10. Thus, pushing the carrier 18 or the secondlattice structure 12 does not necessarily lead to a change in the pitchor braiding angle of the wires 122 of the second lattice structure 12.Thus, by means of the small braiding angle of the carrier 18, squashingtogether of the carrier 18 is avoided during a distal movement of thecarrier 18.

After complete expansion of the tubular body 10, the carrier 18 or thesecond lattice structure 12 has a greater lengthwise extent than the net19 or the first lattice structure 11. The net 19 is therefore subject toa greater foreshortening effect than the carrier 18, such that thecarrier 18, in the expanded state of the tubular body 10, is not coveredcompletely by the net 19 but only partially or in some sections (FIG.10). In the compressed state, the net 19 is longer than the carrier 18.In the expanded state, the length of the net 19 and of the carrier 18can correspond to each other or the difference in length can diminish.

As a result of the different braiding angles between the first latticestructure 11 and the second lattice structure 12, the first latticestructure 11 and the second lattice structure 12, or the net 19 and thecarrier 18, have a different behavior during pulsation of the vessel. Inthe implanted state inside the blood vessel 30, a gap 16 can formbetween the first lattice structure 11 and the second lattice structure12 or between the net 19 and the carrier 18, in particular during thesystole. As a result of the elongation E of the blood vessel 30 duringthe systole, the foreshortening effect means that the carrier 18, whichhas a comparatively small braiding angle, is narrowed at least in somesections, or has a narrowing R at least in some sections. By contrast,during the systole and the elongation E of the blood vessel, the net 19exhibits no narrowing R, or at least much less narrowing R. Thus, a gap16 or an interstice or cushion forms between the carrier 18 and the net19. FIG. 11 shows as an example the behavior of the lattice structures11, 12, or of the carrier 18 and net 19, with different braiding anglesduring an elongation E of the blood vessel.

The net 19 is preferably adapted such that the net 19 can follow thepulsation of the blood vessel 30. In particular, the net 19 has anincreased mobility with respect to the carrier 18, which can beachieved, for example, by suitably small wire diameters and/or suitableadjustment of the braiding angle. During the systole, i.e. the rise inblood pressure, a through-flow F_(D) is brought about, with bloodflowing out of the blood vessel 30 into an aneurysm 31 and leading to avolume increase in the aneurysm 31. The high degree of expansibility ofthe net 19 allows a portion of the net to move radially outward or bedeflected radially outward, with the net 19 following the movement ofthe blood in some sections. A flow of blood through the meshes of thenet 19 is thus impeded. The expansibility of the net 19 is preferablyadjusted such that the net 19, in terms of its deflection by the bloodstream into the aneurysm 31, has an inertia or a resistance to the bloodstream. The net 19 thus follows the rise in blood pressure during thesystole by means of a radially outward movement. The flow of bloodthrough the meshes of the net 19 into the aneurysm 31 is at the sametime reduced. FIG. 12 shows the radial deflection of the net 19 in somesections, under the influence of the systolic rise in blood pressure.The transfer of pressure takes place only to a certain extent, thusresulting in clot formation and reduced degeneration of the cells. Thetransfer of pressure can be controlled by means of the possibility ofbeing able to adjust the expansibility of the net 19, for examplethrough the choice of the braiding angle.

The deflection of the net 19 into the aneurysm 31 has severaladvantages. On the one hand, the flexible net 19 permits the transfer ofthe pressure wave into the aneurysm. Although a stream of blood into theaneurysm is impeded, the pressure P is, by contrast, transferred intothe blood volume of the aneurysm 31. A periodic loading of the cells ofthe aneurysm wall 34 is thus maintained, thereby counteracting adegeneration of the cells. At the same time, the direct through-flow ofblood, i.e. the through-flow F_(D), is reduced, thereby promoting theendothelialization of the tubular body 10. The colonization ofendothelial cells and the adherence of the endothelial cells to thetubular body 10 is made easier by the reduced through-flow F_(D). Inparticular, the closure of the meshes of the lattice structures 11, 12is made easier, since there is only a slight through-flow F_(D), if any,through the meshes of the first lattice structure 11 or of the net 19.

It has generally been shown that it is advantageous to make available alattice structure which is flexible in such a way that it can bedeflected at least in some sections into the aneurysm 31. This is madepossible, for example, by a lattice structure which has a comparativelysmall braiding angle. However, a lattice structure of this kindexperiences increased narrowing R if the blood vessel 30, for example onaccount of the pulsation, is subject to an elongation E. Latticestructures with a large braiding angle do not exhibit this effect.Specifically, a lattice structure with a large braiding angle permitsconsiderable elongation, without any significant change of thecross-sectional diameter. However, lattice structures of this kind donot permit outward bulging in some sections, for example into ananeurysm 31.

Both effects are achieved with the device according to the invention,the functions being assigned to different lattice structures 11, 12. Thesecond lattice structure 12 or the carrier 18 permits the precise andreliable positioning of the tubular body 10 in the blood vessel 30. Bycontrast, the net 19 makes it possible to influence the flow of bloodinto the aneurysm 31, while at the same time permitting a transfer ofthe blood pressure. The post-operative risk of a rupture of the aneurysm31 is thus reduced.

FIG. 7 shows a further illustrative embodiment of the medical device,wherein the net 19 or the first lattice structure 11 has differentbraiding angles. In particular, the first lattice structure 11 comprisesa middle section 111 and two edge sections 116, wherein the middlesection 111 is arranged between the edge sections 116. In the middlesection 111, the first lattice structure 11 has a smaller braiding anglethan in the edge sections 116. The comparatively larger braiding anglein the edge sections 116 has the effect that the edge sections 116compensate for the elongation E of the blood vessel 30, because they areable to undergo elongation without a significant change of diameter. Inparticular, transition sections 113 form between the middle section 111and the edge sections 116, which transition sections 113 are highlightedby the dotted lines in FIG. 7. In the transition sections 113, ashortening K takes place in an orientation counter to the elongation Eof the blood vessel 30. The middle section 111 has a greaterexpansibility than the edge sections 116, such that the middle section111, under the influence of a systolic rise in blood pressure, can havea greater shortening than the edge sections 116. The middle section 111can thus follow the rise in blood pressure, such that the net 19 or thefirst lattice structure 11 in the middle section 111 can bulge out intothe aneurysm 31 or can form a bulge B. For the sake of clarity, thecarrier 18 or the second lattice structure 12 is not shown in FIG. 7.

A further illustrative embodiment is shown in FIG. 13, wherein provisionis made that the net 19 has a shorter lengthwise extent than the carrier18. Particularly in the implanted state inside the blood vessel 30, thenet 19 or the first lattice structure 11 has a substantially shorterlengthwise extent than the carrier 18 or the second lattice structure12. Preferably, the tubular body 10 is positioned in the blood vessel 30in such a way that the distal end 115 of the first lattice structure 11or of the net 19 is arranged in the area of the aneurysm neck 32. Thedistal end 115 of the first lattice structure forms a free end. Bycontrast, the proximal end 110 of the first lattice structure 11 isconnected to the proximal end 120 of the second lattice structure 12.The free end or distal end 115 of the first lattice structure 11 canexpand radially outward. The distal end 115 of the first latticestructure 11 or of the net 19 is thus deflected radially outward intothe aneurysm 31 or into the area of the aneurysm neck 32. In otherwords, the net 19 can be deflected in some sections into the aneurysm31. During a systolic rise in blood pressure, the net 19 therefore moveswith the blood pressure increase into the aneurysm 31, such that thethrough-flow F_(D) through the meshes of the net 19 is reduced. Thedistal end is longer and ensures the adherence.

A further illustrative embodiment is shown in FIG. 14, wherein thetubular body 10 comprises a circumferential wall which has an innerlayer 15 and an outer layer 14. The inner layer 15 is formed by thesecond lattice structure 12, which is designed as carrier 18. The outerlayer 14 has the first lattice structure 11 and a third latticestructure 13, wherein the first lattice structure 11 and the thirdlattice structure 13 each form a net 19. The first and third latticestructures 11, 13 are each connected with their proximal ends 110, 130to the second lattice structure 12. The distal ends 115, 135 of thefirst lattice structure 11 and of the third lattice structure 13 arearranged free. The proximal end 130 of the third lattice structure 13 isconnected to the second lattice structure 12 substantially at the levelof the distal end 115 of the first lattice structure 11. This resultssubstantially in a scale-like arrangement of the first and third latticestructures 11, 13. The first lattice structure 11 and the third latticestructure 13 can also overlap each other at least in some sections orcan be arranged at a distance from each other.

The first lattice structure 11 and the third lattice structure 13, orthe nets 19, can have a valve-like function. By means of the freemobility of the distal ends 115, 135, the nets 19 or the first and thirdlattice structures 11, 13 permit a certain transfer of pressure into theaneurysm 31. At the same time, the valve function of the nets 19 permitsthe delivery of additional treatment devices into the aneurysm 31. Suchtreatment devices can comprise a coil catheter 21, for example.

In principle, the invention is not limited to two nets 19 or two latticestructures 11, 13 that form the outer layer 14. Instead, provision isalso made, within the context of the invention, that three or more nets19 or lattice structures 11, 13 form the outer layer 14 of thecircumferential wall of the tubular body 10.

FIG. 15 a shows a further illustrative embodiment, which differs fromthe illustrative embodiment according to FIG. 14 in that the firstlattice structure 11 and the third lattice structure 13 are orientedsubstantially in opposite directions. Specifically, in the illustrativeembodiment according to FIG. 15 a, provision is made that the firstlattice structure 11 comprises a proximal end 110 which is connected tothe proximal end 120 of the second lattice structure 12. The distal end115 of the first lattice structure 11 is arranged free. By contrast, thethird lattice structure 13 comprises a distal end 135 which is connectedto the distal end 125 of the second lattice structure 12. The proximalend 130 of the third lattice structure 13 is arranged free. Moreover, inthe illustrative embodiment according to FIG. 15 a, provision is madethat the free ends, i.e. the distal end 115 of the first latticestructure 11 and the proximal end 130 of the third lattice structure 13,overlap each other. This applies at least to the expanded or implantedstate of the tubular body 10. Alternatively, provision can also be madethat the first and third lattice structures 11, 13 do not overlap eachother in the expanded or implanted state of the tubular body 10 andinstead are arranged in alignment with each other, as is shown in FIG.16 a.

Moreover, in the illustrative embodiment according to FIG. 15 a,provision is advantageously made that the nets 19, or the first andthird lattice structures 11, 13, overlap each other in the expandedstate, but are arranged in alignment with each other in the compressedstate of the tubular body 10. For this purpose, provision isadvantageously made that, during the expansion of the tubular body 10,the carrier 18 or the second lattice structure 12 is shortened to agreater extent than the nets 19. At least one net 19 or a plurality ofnets 19 have in particular a smaller braiding angle than the carrier 18,such that the carrier 18 is considerably shortened during the expansionof the tubular body 10, as a result of which the nets 19 overlap in theexpanded state. The overlapping ensures that the aneurysm neck 32 iscompletely covered. At the same time, the mobility of the free ends ofthe first and third lattice structures 11, 13 permits a relativemovement of the two lattice structures 11, 13 or nets 19 to each other,such that an efficient transfer of pressure into the aneurysm 31 isenabled. At the same time, the overlapping of the first and thirdlattice structures 11, 13 in some sections increases the fineness of themesh in the area of the aneurysm neck 32 and has an advantageousinfluence on the flow of blood into the aneurysm 31. By contrast, toachieve this kind of mesh fineness with a single net 19 or a singlelattice structure 11, a comparatively larger delivery system 20 isneeded.

The aligned arrangement of the nets 19 inside the delivery system 20,i.e. in the compressed state, reduces the crimp diameter, such thatsmall delivery systems 20 can be used (FIG. 15 b).

In the illustrative embodiment according to FIG. 16 a, provision is madethat, in contrast to the illustrative embodiment according to FIG. 15 a,the mutually opposite nets 19 or the first and third lattice structures11, 13 have a comparatively larger braiding angle. This increases thefine mesh of the individual nets 19 or of the first and third latticestructures 11, 13. A configuration of this kind has the effect that thenets 19 shorten to a great extent during the expansion. In order topermit an exact positioning of the tubular body 10 in the blood vessel,the carrier 18 or the second lattice structure 12 advantageously has, bycontrast, a comparatively small braiding angle, such that theforeshortening effect is reduced.

In the expanded or implanted state of the tubular body 10, the firstlattice structure 11 and the third lattice structure 13 or the two nets19 are preferably arranged in alignment with each other. The free endsof the first and third lattice structures 11, 13 can touch each other,such that the aneurysm 31 or the aneurysm neck 32 is completely coveredby the first and third lattice structures 11, 13. In the compressedstate inside the delivery system 20, by contrast, the first and thirdlattice structures 11, 13 are superposed, as is shown in FIG. 16 b. Inorder to achieve the smallest possible compressed cross-sectionaldiameter despite the superposing or overlapping of the first and thirdlattice structures 11, 13 in the delivery system 20, provision is madethat the nets 19, or the first and third lattice structures 11, 13, havea small number of wires. As a result of the comparatively large braidingangle that the first and third lattice structures 11, 13 adopt in theblood vessel 30, a very fine-meshed structure is guaranteed even with asmall number of wires. Moreover, the cross-sectional diameter in thecompressed state of the tubular body 10 is reduced on account of thesmall number of wires. The nets can also be arranged on the inside.

As has already been described, the adoption of different braiding anglesin separate layers 14, 15 of the tubular body permits the formation of agap 16 between the layers 14, 15. In particular, in the expanded stateof the tubular body 10, the net 19 can lift away from the carrier 18.The formation of a gap in a suitably configured medical device is shownin FIG. 17. The gap 16 permits additional influence of the flowconditions in the aneurysm 31. By means of the gap 16, or the distancebetween the net 19 and the carrier 18, a cushion is basically obtainedin which flow eddies arise that are produced by shear stresses betweenthe blood inside the cushion or gap 16 and the vessel flow F_(G). As aresult of the flow eddies in the gap 16, an energy loss occurs, by whichmeans the flow velocities inside the aneurysm 31 are reduced. Inparticular, the vessel flow F_(G) does not cause a direct eddy flowF_(W) in the aneurysm but initially an eddy flow in the gap 16. Althoughan exchange of blood is permitted between the blood vessel 30 and theaneurysm 31, the flow velocities are reduced. At the same time, theexpansibility of the net 19 permits a transfer of pressure into theaneurysm 31, such that, in order to preserve the cells of the aneurysmwall 34, nutrients are conveyed to the cells via the blood and,moreover, a mechanical stress is maintained that counteractsdegeneration. At the same time, the net may permit a reduced or moderatetransfer of pressure.

An illustrative embodiment of an overall system or of a device withcarrier 18 and net 19 is shown in FIG. 18. The device according to FIG.18 forms a retractable braid on account of the oblique tip in theproximal area of the device. The device is a stent, in particular ananeurysm stent. The basic design of the device, particularly in the areaof the oblique tip, is disclosed in DE 10 2009 056 450 filed by theapplicant. The basic design entails a braid of wire elements with aseries of end meshes or end loops which delimit an axial braid end,wherein the end meshes comprise outer wire elements which form aterminal edge 46 of the braid and merge into inner wire elementsarranged inside the braid. A first section of the terminal edge 46 and asecond section of the terminal edge 46 in each case have several outerwire elements which together form a peripheral border of the terminaledge 46. The border is adapted in such a way that the axial braid end ofthe hollow body can be drawn into a delivery system. The outer wireelements of the first section for forming the terminal edge 46 arearranged immediately downstream of the latter and each have a firstaxial component extending in the longitudinal direction of the hollowbody. The outer wire elements of the second section for forming theterminal edge 46 are arranged in immediate succession along the latterand each have a second axial component which extends in the longitudinaldirection of the hollow body and is counter to the first axialcomponent. Both axial components are referred to the same peripheraldirection of the border.

This configuration of the proximal end of the device applies to all theillustrative embodiments of this application in which the device has anoblique tip pointing in the proximal direction.

In the illustrative embodiment according to FIG. 18, the first latticestructure 11 of the net 19 is arranged congruently over the secondlattice structure 12 of the carrier 18. The second lattice structure 12of the carrier 18 is therefore visible only in the area of the net 19where the strands or individual wires of the two lattice structures 11,12 are not congruent. The strands or wires of the second latticestructure 12 of the carrier 18 are indicated in black in the area of thenet 19 and have a larger diameter than the wires of the net 19.

In the area of the proximal tip or at the proximal end 110 of the firstlattice structure 11, and at the distal end 115 of the first latticestructure 11, the two lattice structures 11, 12 are congruent, such thatonly the first lattice structure 11 shown on top in FIG. 18 can be seen.The second lattice structure 12 is arranged underneath the first latticestructure 11 in the developed view. In the tubular (three-dimensional)body 10, the first lattice structure 11 with the net 19 is arrangedradially to the outside and the second lattice structure 12 of thecarrier 18 is arranged radially to the inside.

The transition from the net 19 to the strands in the area of the tip ofthe first lattice structure 11 is such that in each case four individualwires of the net 19 or four individual strands of the net 19 are broughttogether to form two strands, which are in turn brought together in theproximal direction to form one strand, from which the lattice structureof the tip is formed. Another number of wires or strands, eachsuccessively combined with one another or brought together, is possible.The strands guided in the proximal direction extend into the terminaledge 46 and are connected there as per DE 10 2009 056 450.

The area of the tip of the carrier 19 is configured accordingly, whereinthe lattice structure 12 of the carrier 18 is formed from individualwires with a larger diameter than the individual wires of the firstlattice structure 11. Alternatively, the second lattice structure 12 canalso be formed from several strands that each consist of individualwires.

In the area of the tip, therefore, the strands or wires of the twolattice structures 11, 12 run in parallel and are congruent. The sameapplies to the distal end 115.

In the area of the net 19, the wires or strands likewise run inparallel, but they are not congruent. Instead, the wires of the net 19overlap the lattice cells formed by the carrier 18.

In the illustrative embodiment according to FIG. 18, the punctiformconnection between the first lattice structure 11 and the second latticestructure 12 takes place outside the two lattice structures 11, 12.Specifically, the two lattice structures 11, 12 are connected in thearea of the two common end strands 43, 44 in which all the wires of therespective lattice structures 11, 12 are brought together. The two endstrands 43, 44 are shown in cross section in FIG. 19. The connection isprovided by the sleeve 17. Instead of the sleeve 17, the two end strands43, 44 can be connected in some other way. For example, the thinnerwires of the first lattice structure 11, which forms the outer layer inthe illustrative embodiment according to FIG. 18, can be mounted ontothe thicker wires of the carrier 18 and, for example, twisted. Forexample, the thicker wires of the carrier 18 are twisted together in aninner strand. The thinner wires of the net 19 or of the first latticestructure 11 are twisted radially to the outside on the inner strand.Other types of connection are possible. In addition or alternatively,the wires can be connected by a sleeve, for example by the sleeve 17according to FIG. 19. The sleeve can be crimped onto the wires and/orwelded to the wires. The wires can be twisted and connected as describedabove. Alternatively, the wires can also be arranged loosely alongsideeach other. The strands of both lattice structures 11, 12 can also bearranged alongside each other, wherein the sleeve 17 encloses andconnects both strands, as is shown in FIG. 19. The sleeve 17 can becircular or oval in cross section, for example as is shown in FIG. 19.The oval contour promotes the apposition to the vessel wall.

The punctiform connection of the two lattice structures 11, 12 outsidethe surface of the lattice structures 11, 12 has the effect that thelattice structures 11, are arranged loosely one above the other and aretherefore movable relative to each other. At the same time, the twolattice structures 11, 12 are oriented such that the patterns of thelattice structures 11, 12 in combination with each other form ahigher-order common pattern, as can be seen clearly in FIG. 18.

The connection between the two lattice structures 11, 12 or the twobraids can also take place in the area of the loops. For example, thethin wires of the net 19 can be wound around the thicker wires of thecarrier 18 or twisted together with them. This applies for each numberof wires. For example, each loop of the net 19 consists of two wireswhich are wound about the single wire of the loop of the carrier 18.Another number of wires or wire combinations is possible. The connectionof the wires by sleeves is also possible.

Further possibilities for the punctiform connection of the two latticestructures 11, 12 include the connection being made only in the area ofthe terminal edge 46, for example by twisting. Another punctiformconnection can be obtained by means of the wires of the two latticestructures 11, 12 being twisted together, or otherwise connected, forexample welded, in the whole oblique area or in the whole area of thetip. The area of the tip terminates where the two lattice structures 11,12 merge into the area of the closed cylindrical jacket surface. Thedistal end can correspondingly have a punctiform connection between thetwo lattice structures 11, 12.

A further illustrative embodiment of a device according to the inventionis shown in FIG. 21, in which a carrier 18 according to FIG. 20 is used.The carrier 18 according to FIG. 20 is adapted to be connected in amiddle area to a further braid, in particular to a further latticestructure. For this purpose, the second lattice structure 12 of thecarrier 18 has anchoring sites 45 at which the first lattice structure11 can be secured to the net 19. The basic design of the latticestructure 12 of the carrier 18 corresponds to the basic design accordingto FIG. 18 or DE 10 2009 056 450, at least as regards the area of thetip.

In the area of the anchoring sites 45, the wires of the carrier 18 aretwisted and extend substantially parallel to the longitudinal axis ofthe device.

The combined structure is shown in FIG. 21, where the first latticestructure 11 with the net 19 is arranged radially to the outside, andthe carrier 18 radially to the inside, in the tubular(three-dimensional) body 10. The first lattice structure 11 with the net19 partially overlaps the second lattice structure 12, there being nooverlap in the area of the tip or terminal edge 46. Therefore, in FIG.21, the lattice structure 12 of the carrier 18 is visible in the area ofthe tip. As in the illustrative embodiment according to FIG. 18, thelattice structure 12 of the carrier 18 continues in the area of the net19 and is clearly visible under the net 19 by means of the thicker wiresor strands that are shown in black. At the distal end 115, the end loopsof the first lattice structure 11 cover the distal end of the secondlattice structure 12 of the carrier 18.

The punctiform connection of the two lattice structures 11, 12 isachieved by means of the wires of the net structure 19 converging in thearea of the twisted elements of the carrier or of the anchoring sites45. In the area of the anchoring sites 45, the wires of the two latticestructures 11, 12 run parallel to each other and are oriented parallelto the axis of the stent. In the area of the anchoring sites 45, thewires can be twisted or connected in some other way, for example bywelding, adhesive bonding, soldering, or by a separate means such as aconnecting sleeve, in particular a c-shaped connecting sleeve. Thec-shaped connecting sleeve has the advantage that the two systems orlattice structures 11, 12 can initially be overlapped during productionand then connected by the sleeve. Alternatively, the thinner wires ofthe net 19 can be wound around the thicker wires of the carrier 18 ortwisted together with them, specifically in the area of the anchoringsites 45.

Alternatively, the connection can also be made at intersections of thecarrier 19. A common aspect of these embodiments is that the connectionof the two lattice structures 11, 12 is punctiform, i.e. not across theentire surface of the two lattice structures, and instead only within alimited area. The punctiform connection according to FIG. 21 is a linearconnection in the circumferential direction and is composed ofindividual connection points or connection sites. The connection pointsare formed, for example, at the anchoring sites 45, where the twolattice structures are connected locally to each other to a limiteddegree.

The distal end of the net 19 can have open ends. The advantage of thisis the ease of production. However, the distal end can also have closedloops. In addition to the proximal connection in the area of theanchoring sites 45, a punctiform connection can also be made at thedistal end of the net.

The invention is suitable for endovascular interventions, particularlyfor the treatment of aneurysms in blood vessels. For this purpose, themedical device is preferably designed as a stent. The invention is notlimited to a medical device or a stent that comprises braided latticestructures. Instead, the lattice structures can also be formed bycutting a corresponding structure from a solid material, particularlyfrom a tubular solid material. The use of lattice braids or wire braidsis advantageous in view of the preferred fine-meshed structure.

FIGS. 22 and 23 show that the multiple braid, with an outer braid orouter layer 14 relatively movable in the axial direction and radialdirection, is suitable for the treatment of different types ofaneurysms. As is shown, the multiple braid is suitable for the treatmentof fusiform aneurysms, which develop in a spindle shape all the wayaround the vessel circumference. In a fusiform aneurysm, the inner layer15 or the second lattice structure 12 forms, as has been describedabove, the carrier 18 which positions the system in the vessel. As isshown in FIG. 22, the inner layer 15 bears on the vessel wall 35upstream and downstream of the aneurysm 31 that is to be treated. Theouter layer 14 expands uniformly on the entire circumference of thetubular body 10 and lifts away from the latter, as is shown in FIG. 22.In this way, an annular gap 16 forms in the area of the fusiformaneurysm and ensures the eddying of the blood stream in this area. Thelocally limited securing of the outer layer 14 on the one hand and thelow stiffness of the outer layer 14 on the other hand permit thespindle-shaped expansion of the outer layer 14, such that the outerlayer 14 protrudes at least partially into the fusiform aneurysm. Thepossibilities of locally limited securing are described above and aredisclosed in connection with this illustrative embodiment. The stiffnessof the outer layer 14 is less than the stiffness of the inner layer 15.The outer layer 14 is more flexible than the inner layer 15.

In a lateral aneurysm (saccular aneurysm), the outer layer 14 moveslaterally away from the inner layer 15, as is shown in FIG. 12 forexample. The outer layer 14 is therefore pressed away from the side onwhich there is no aneurysm and bulges into the neck of the aneurysm.

The function of the multiple braid as described in connection with FIG.22 is disclosed and claimed in connection with all of the illustrativeembodiments.

The bulging or widening of the outer layer 14 or of the outer braid canbe set automatically by suitable conditioning in the context of a heattreatment when the tubular body 10 is released from the catheter. Thismeans that the outer braid or the outer layer 14 is widened in the reststate and thus lifts away from the inner layer 15. The widening of theouter braid can be stamped on a middle area of the outer braid orstamped exclusively on a middle area of the outer braid. As is shown inFIG. 22, the shape of the widening can be adapted for the treatment of afusiform aneurysm and can extend in an annular shape around the tubularbody 10 or have a spindle shape. Alternatively, the shape of thewidening can be adapted to the treatment of a saccular aneurysm and formexclusively to the side or only on one side of the body 10. The outerlayer 14 or the outer braid can, for example, be shaped and heat-treatedon a suitably curved mandrel. The braid ends or the end areas of thebraid of the outer layer 14 remain in contact with the braid of theinner layer 15. This means that the end areas of the outer layer 14 arelocated on the same plane or the same jacket surface as the braid of theinner layer 15. In the middle area, or generally between the end areas,the braid of the outer layer 14 lifts away from the inner layer 15.

Alternatively or in addition, the widening, as has been described above,can be obtained from the different braiding angle between the innerlayer 15 and the outer layer 14 or between the respective braids.

The above-described constrained widening of the outer layer 14 bysuitable heat treatment is disclosed and claimed as a possible option inconnection with all of the illustrative embodiments. Moreover, it isdisclosed and claimed in this connection that at least the outer layer14 or the braid of the outer layer 14 is produced from a shape-memorymaterial, for example from nitinol or another shape-memory materialcustomarily used in medical engineering and permitting a heat-inducedchange of shape. Alternatively, the constrained change of shape can alsobe obtained by an elastic deformation of the braid of the outer layer14.

As has been explained above, the braid of the outer layer 14 or theouter braid can lift away from the inner layer 15, because the outerlayer 14 is relatively soft or more flexible than the inner layer 15 andcan move in the flow. Alternatively, the braid of the outer layer 14 canhave a stable structure. In particular, the braid of the outer layer 14can have reinforcing wires, which limit the radial mobility of the braidof the braid of the outer layer 14. In this way, a stable gap formsbetween the outer layer 14 and the inner layer 15, and the braid of theouter layer 14 moves very little, if at all, in the blood stream. Inthis embodiment, the radial stability or stiffness of the outer layer 14corresponds approximately to the radial stability or stiffness of theinner layer 15. This means that more or less the same forces are neededto widen the outer layer 14 and to widen the inner layer 15. The stableouter braid or the stable outer layer 14 is suitable in particular inconnection with the above-described embodiment in which the shape of theouter layer 14 in the rest state is curved radially outward or in whichthe outward curvature is stamped on and the gap 16 between the outerlayer 14 and the inner layer 15 forms automatically upon release fromthe catheter. The automatic formation of the gap 16 means generally thatthe widening of the outer layer 14 is effected by internal forces or atleast predominantly by internal forces of the outer layer 14. Thisprocess can be assisted by the external forces applied by the bloodflow. However, in this embodiment, the widening is primarilyattributable to the properties of the shape-memory material and theassociated internal forces.

FIG. 23 shows another illustrative embodiment of the invention in whichthe braid of the outer layer 14, or generally the outer layer 14, has anundulating contour in cross section. Generally, the distance between theouter layer 14 and inner layer 15 varies, with the distance alternatelyincreasing and decreasing. The undulating contour is particularlyeffective in slowing down the flow in the aneurysm 31. The undulatingstructure can have at least two peaks and, lying between these, avalley. In the illustrative embodiment according to FIG. 23, theundulating contour is formed with four peaks. Another number of peaks ispossible. As can be seen in FIG. 23, the peaks have different heights.The height of the peaks decreases in the proximal and distal directionsof the tubular body 10. The peaks are highest in the middle area of theundulating contour. The outer contour of the peaks, which is defined bytheir points or sections farthest away from the inner layer 15,corresponds approximately to the shape of the aneurysm that is to betreated. The outer contour (enveloping surface) of the undulatingcontour is adapted to the shape of the aneurysm.

At least some of the valleys can be spaced apart from the inner layer15. It is possible for all the valleys to be spaced apart from the innerlayer 15. Alternatively, at least some of the valleys can touch theinner layer 15. It is possible for all of the valleys to touch the innerlayer 15.

The contact sites between the valleys and the inner layer 15 can beproduced by connections between the braids of the outer layer 14 and ofthe inner layer 15. This applies to some of the valleys or to all of thevalleys. The braid of the outer layer 14 can be connected to the braidof the inner layer 15 at a number of sites spaced apart from each otherin the axial direction. This can be done, for example, by using sleeves,crimp sleeves or other connecting techniques, for example cohesivelybonded connections. The sleeves can be C-shaped, for example, and can befitted subsequently, i.e. after the interweaving to connect the twobraids or the multiple braids.

Alternatively or in addition, the undulating structure can bepreconditioned by heat treatment, such that the undulating structureforms in the rest state. A shape-memory material known per se, forexample nitinol, is used for this. Purely mechanical shaping ispossible, in which case the wave shape is stretched out in the catheterand recovers the undulating rest state after release.

A particularly important aspect of this illustrative embodiment, but oneto which the invention is not limited, is that those areas that are toexpand radially outward have a different braid structure than thoseareas of the undulating contour or of the undulating structure that formthe valleys, in particular those areas that are intended to remain incontact with the braid of the inner layer 15. For example, the braidingangle in the areas that are intended to lift, particularly in the areaof the peaks, can be smaller than the braiding angle of the areas thatare not intended to lift, particularly in the area of the valleys. Abraid that has a relatively small braiding angle can widen comparativelyeasily. During widening, the braiding angle increases on account of theaxial compression during the widening. Those areas that are radiallymore stable and can therefore widen less readily have a larger braidingangle. These are the areas in which the valleys of the structure form.For example, the braiding angle can be larger than 45° in the area ofthe valleys and smaller than 45° in the area of the peaks.

The areas with a small braiding angle, or a smaller braiding angle thanin other areas, are associated with a lower axial shortening duringexpansion. This means a greater radial widening with lower axialcompression. This has the effect that, upon axial compression of theinner layer, the areas with the small braiding angle (peaks) have towiden outward, so that the structure shortens at the same time. Theouter layer has in fact to shorten if it is connected distally to theinner layer or if the inner layer presses it outward onto the vesselwall and therefore blocks it.

Some or all of the aforementioned possibilities for forming theundulating structure can be combined with one another. For example, theundulating structure can be obtained from a combination of heattreatment (pre-embossing of the contour) and/or different braidingangles and/or mechanical connections between the inner layer 15 andouter layer 14.

In connection with the offset of the outer layer 14 relative to theinner layer 15, it is disclosed that the braids can also be offset fromeach other in the rest state. This means that the proximal end of onebraid is offset in the axial direction to the proximal end of the otherbraid. In addition or alternatively, the distal braid ends of the twobraids or of the multiple braids can also be offset from each other inthe axial direction in the rest state. Specifically, the proximal end ofthe braid of the outer layer 14 and/or the distal end of the braid ofthe outer layer 14 can each be axially offset inward with respect to theproximal and/or distal end of the braid of the inner layer 15.

The braid of the outer layer 14 can have at least one and a half timesas many wires as the braid of the inner layer 15, in particular at leasttwice as many wires, in particular at least three times as many wires,in particular at least 4 times as many wires, as the braid of the innerlayer 15. These ranges of the wire numbers are disclosed and claimed inconnection with all of the illustrative embodiments.

The undulating structure has the advantage of great axialcompressibility. In this way, the braid of the outer layer 14 can beadapted well to different aneurysm lengths and widths.

The gap 16, which forms at least during use between the braid of theinner layer 15 and the braid of the outer layer 14, merges continuously,at the proximal and/or distal end of the gap 16, into the jacket surfaceof the tubular body 10. This is shown by way of example in FIG. 12 or inFIG. 22. The same is true in the case of treatment of a saccularaneurysm in the circumferential direction. Here too, the gap or theraised braid area of the outer layer 14 merges continuously into thejacket surface of the body 10. Things are slightly different in thetreatment of a fusiform aneurysm, in which case an annular gap 16extending in the circumferential direction forms, or is preconditioned,between the inner layer 15 and the outer layer 14. The maximum gapwidth, i.e. the distance between the inner layer 15 and the outer layer14, is 50% of the expanded diameter of the tubular body. The expandeddiameter relates to the free tubular body on which no external forcesact, and which is therefore not arranged in the vessel. The minimum gapwidth is 5% of the expanded diameter of the tubular body 10. The samedefinition of the expanded diameter as described above applies here too.Intermediate values of the aforementioned maximum range are possible.For example, the gap width can be at most 45% of the expanded diameter,in particular at most 40%, in particular at most 35%, in particular atmost 30%, in particular at most 25%, in particular at most 20%, inparticular at most 15%, in particular at most 10% of the expandeddiameter. The lower gap range can be at least 5%, in particular at least10%, in particular at least 15%, in particular at least 20% of theexpanded diameter of the tubular body 10. The aforementioned lower andupper limits can be combined with one another.

The device can have several plies which extend in a layered arrangementon the circumference of the body 10 and overlap one another, inparticular partially overlap one another. A gap 16 is formed in eachcase between the individual plies. Two gaps form in the case of threeplies, three gaps in the case of four plies, etc.

Particularly in the treatment of fusiform aneurysms, it is advantageousif the outer ply or the outer layer 14 lies close to the inside wall ofthe aneurysm or even comes into contact therewith. The lattice structureof the outer ply thus stabilizes the wall of the aneurysm and slows downthe flow in the vicinity of the wall.

In addition, an intermediate ply or intermediate layer 14 a can beprovided which, during use, is spaced apart from the inner ply or theinner layer 15 and from the outer ply or the outer layer 14. Theintermediate ply is arranged in the aneurysm during use. The inner plyis flush with the neck of the aneurysm. It is possible to provideseveral intermediate plies or intermediate layers 14 a which protrudeinto the aneurysm and progressively slow down the flow. This design isparticularly suitable for fusiform aneurysms, since these can bedifficult to fill with coils. This affords a simple possibility ofintroducing material in the form of braided layers into the aneurysm.

The braided layers protruding into the aneurysm form outer layers which,as clot-forming layers, contribute to occluding the aneurysm.

The different widening or the different degree of lifting of the layers,and therefore the gap formation between the individual layers, can beachieved by different braiding angles of the layers. In addition oralternatively, the gap formation can be achieved by use of ashape-memory material, by different diameters being stamped on thelayers through a suitable heat treatment known per se.

In the example according to FIG. 24, the outer layer 14 is at leastpartially in contact with the aneurysm wall. The distal end of the outerlayer 14 is located in the aneurysm or at least at the end of theaneurysm neck. The advantage of this configuration, in which the outerlayer 14 does not extend past the aneurysm neck into the vessel, is thatthe distal end of the outer layer 14 can freely expand and the entireouter layer can bear safely on the wall of the aneurysm. Structurally,this is achieved by the fact that the outer layer 14 is axially shorterthan the body 10 and/or an optional intermediate layer 14 a. The outerlayer 14 can be shorter than the body 10 by at least 10%, in particularat least 20%, in particular at least 30%, in particular at least 40%, inparticular at least 50%, in particular at least 60%, in particular atleast 70%.

The distal end of the outer ply or of the outer layer 14 canalternatively extend, like the middle ply, distally beyond the aneurysmneck. Here, the ply is pressed by the inner braid or the inner layer 15against the vessel wall and thus fixed. When the distal end is fixed bythe inner ply or inner layer 15, the expansion of the outer ply or outerlayer 14 into the aneurysm is determined to a greater degree by thebraiding angle.

Therefore, if a defined gap 16 is to be set, the distal end and proximalend must be blocked. For this purpose, a suitably long outer layer 14 isprovided. If the expansion is to be free, in order to bear against thewall, the length of the outer layer 14 must be chosen such that there isno blocking of the outer layer 14.

Generally, only the proximal ends of the plies or layers 14, 14 a, 15are interconnected. The blocking of the distal ends, if desired, isobtained by friction during use. This design is a technically simpleone. The braid distorts only slightly. If the blocking at the distal endis obtained by friction, the braids can shift relative to one anotherduring the positioning, specifically at the distal end, which reducesthe danger of distortion and promotes adaptation to the anatomy.

By contrast, if the distal end of the layers is connected, secureblocking is achieved and the gap formation can be controlled withprecision by the different braiding angles.

These observations also relate to the case where the body 10 is composedof only 2 plies, namely the inner layer 15 and the outer layer 14, or ofmore than 2 or 3 plies, etc.

LIST OF REFERENCE SIGNS

-   10 tubular body-   11 first lattice structure-   12 second lattice structure-   13 third lattice structure-   14 outer layer-   14 a intermediate layer-   15 inner layer-   16 gap-   17 connecting sleeve-   18 carrier-   19 net-   20 delivery system-   21 coil catheter-   30 blood vessel-   31 aneurysm-   32 aneurysm neck-   34 aneurysm wall-   35 vessel wall-   36 attack region-   40 conventional aneurysm stent-   41 first wire-   42 second wire-   43 end strand of the first lattice structure 11-   44 end strand of the second lattice structure 12-   45 anchoring sites-   46 terminal edge-   110 proximal end of the first lattice structure 11-   111 middle section-   112 wire of the first lattice structure 11-   113 transition section-   115 distal end of the first lattice structure 11-   116 edge section-   120 proximal end of the second lattice structure 12-   122 wire of the second lattice structure 12-   125 distal end of the second lattice structure 12-   130 proximal end of the third lattice structure 13-   135 distal end of the third lattice structure 13-   F_(G) vessel flow-   F_(W) eddy flow-   F_(D) through-flow-   B bulge-   E elongation of the blood vessel 30-   K shortening of the transition section 113-   P pressure-   W widening of the blood vessel 30-   R narrowing

1. A medical device, comprising a body which is tubular at least in somesections, can be transferred from a compressed state to an expandedstate and has a circumferential wall with at least a first latticestructure and a second lattice structure, wherein the first latticestructure and the second lattice structure form separate layers of thecircumferential wall, which layers are arranged coaxially one inside theother and are connected to each other at least at points, in such a waythat the first lattice structure and the second lattice structure aremovable relative to each other at least in some sections.
 2. The medicaldevice as claimed in claim 1, wherein the first lattice structure and/orthe second lattice structure is formed in each case from interwovenwires.
 3. The medical device as claimed in claim 1, wherein the firstlattice structure has a proximal end, which is connected to a proximalend of the second lattice structure in such a way that distal ends ofthe first and second lattice structures arranged opposite the proximalends are movable relative to each other.
 4. The medical device asclaimed in claim 1, wherein the first lattice structure and the secondlattice structure, in a production state, have braiding angles that arethe same at least in some sections or different from one another.
 5. Themedical device as claimed in claim 4, wherein the braiding angle of thefirst lattice structure and/or of the second lattice structure is atmost 70°, in particular at most 65°, in particular at most 60°, inparticular at most 59°, in particular at most 57°, in particular at most55°, in particular at most 52°, in particular at most 50°.
 6. Themedical device as claimed in claim 1, wherein, in a radially expandedstate of the tubular body, a gap is formed at least in some sectionsbetween the first lattice structure and the second lattice structure. 7.The medical device as claimed in claim 1, wherein the first latticestructure and the second lattice structure each have closed meshes,wherein the size of the meshes of the first lattice structure isdifferent than the size of the meshes of the second lattice structure.8. The medical device as claimed in claim 2, wherein the wires of thefirst lattice structure have a smaller cross-sectional diameter than thewires of the second lattice structure.
 9. The medical device as claimedin claim 2, wherein the first lattice structure has a greater number ofwires than the second lattice structure.
 10. The medical device asclaimed in claim 1, wherein the first lattice structure forms an outerlayer and the second lattice structure forms an inner layer of thetubular body.
 11. The medical device as claimed in claim 1, wherein thefirst lattice structure has an axial lengthwise extent that is smallerthan an axial lengthwise extent of the second lattice structure, in sucha way that the first lattice structure covers the second latticestructure in some sections, in particular by at least 20%, in particularby at least 30%, in particular by at least 40%, in particular by atleast 50%, in particular by at least 60%.
 12. The medical device asclaimed in claim 1, wherein the tubular body has a third latticestructure which together with the first lattice structure forms theouter layer of the tubular body.
 13. The medical device as claimed inclaim 12, wherein the first lattice structure is connected at a proximalend, and the third lattice structure at a distal end, to the secondlattice structure which forms the inner layer of the tubular body. 14.The medical device as claimed in claim 12, wherein the first latticestructure and the third lattice structure overlap at least in somesections in a radially compressed state or a radially expanded state.15. The medical device as claimed in claim 12, wherein the first latticestructure and the third lattice structure each comprise a proximal end,which is connected to the second lattice structure, wherein the proximalend of the first lattice structure is arranged at a distance from theproximal end of the third lattice structure.
 16. The medical device asclaimed in claim 1, wherein the first lattice structure comprises amiddle section and two edge sections delimiting the middle section,wherein the first lattice structure has a smaller braiding angle in themiddle section than in the edge sections.
 17. The medical device asclaimed in claim 10, wherein the distance between the outer layer andthe inner layer varies in the expanded state of the body, wherein thedistance alternately decreases and increases at least in some sections.18. The medical device as claimed in claim 17, wherein the outer layer,in the expanded state of the body, has an undulating contour at least insome sections.
 19. The medical device as claimed in claim, wherein theouter layer 14 has alternately disposed peaks and valleys, wherein atleast some, in particular all, of the valleys are connected to the innerlayer and/or are preshaped, in particular preshaped by heat treatment,and/or have another braiding angle than the peaks.
 20. A system formedical uses, with a device as claimed in claim 1, and with a deliverysystem which comprises a flexible delivery element, in particular aguide wire, wherein the delivery element is connected or connectable tothe device.